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ALLLMINUM AS A FACTOR IN SOIL ACIDITY 



JOSE JISON MIRASOL 

B.S. University of the Philippines, 1915 
M.S. University of the Philippines, 1917 



THESIS 



Submitted in Partial Fulfillment of the Requirements for the 
Degree of 



DOC^rOR OF PHILOSOPHY 
IX AGUONOiMY 



THK CKADUATE .SCIIOOI, 
OF THE 

UNIVERSITY OF ILLINOIS 
1920 



Aluminum as a Factor in Soil Acidity 



BY 

JOSE JISON MIRASOL 

B. S. University of the Philippines, 1915 
M. S. University of the Philippines, 1917 



Thesis Submitted in Partial Fulfillment of the Requirements 

for the Degree of Doctor of Philosophy in Agronomy in 

The Graduate School of the University 

of Illinois, 1920 



Reprinted from Soil Science, Vol. 10, No. 3, September, 1920. 







FEB 281921 



^ 



TABLE OF CONTENTS 



C 



•o I. Introduction 153 

II. Opinions Concerning the Cause and Nature op Soil Acidity 155 

1. The Presence of True Acids 155 

'^ 2. The Adsorption Theory of Soil Acidity 157 

J) 3. The Presence of Soluble Salts of Aluminum in the Soil 158 

III. Aluminxjm in Agriculture 158 

1. Aluminum in Plants 159 

a. Physiological action of aluminum on plants 159 

2. Aluminum Salts as Stimulants and I^'ertilizers 160 

.5. .\luminum in the Soil 162 

a. Aluminum in the subsoil 163 

b. Distributi(m of aluminum in the soil separates 163 

c. The aluminum compound in the soil that gives rise to soluble alu- 

minum salts 164 

d. Lateritization in northern climates 164 

1\'. Experimental 165 

1. The Problem 165 

2. The General Plan of the Work 166 

3. Description of the Material Used 166 

a. Gray silt loam 167 

b. Yellow gray silt loam 167 

c. Yellow silt loam 167 

4. Experiment I. Effect of Aluminum Salts, Alone and in Combination with 

Calcium Carbonate or with Acid Phosphate on Sweet Clover Grown 

in Sand 169 

a. Plan of the experiment 171 

b. Results and Discussion 1 73 

(I) The effect of aluminum salts on sweet clover in the presence 

of calcium carbonate 174 

(II) The effect of aluminum salts on sweet clover in the presence 

of acid phosphate 175 

,S. Experiment II. I^ffect of Limestone and Acid Phosphate Alone and in 

Combination, on the Productivity and Acidity of .\cid Soils 176 

a. Plan of the experiment 1 76 

I), Results and Discusssion 177 

(I I How acid phosphate reduces the aciditj' of acid soils 180 

ft. Experiment III. What Happens When .-Vcid Soils are Leached-out with 

Potassium Nitrate before and after the Application of Limestone 182 

a. Discussion of results 183 

b. Sweet clover on leached soils 184 

c. How aluminum salts arise in the soil 185 

d. What happens when acid soils are extracted with potassium nitrate 

before and after the application of limestone 180 

7. E.\'periment IV. Iron and Manganese as Factors in Soil Acidity 187 

V. SUMM.\RY . . . 188 

\T. .Acknowledgment 190 

VII. References 190 

VIII. Pl.\tes ; iQ-i 

IX. Vita 219 



Reprinted from Soil Science, 
Vol. X, No. 3, September, ]9;0 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 

JOSE JISON .AIIRASOL 

Universily of Illinois 
Received for publication June 21, 1020 
I. INTRODUCTION 

In 1902, the late Dr. Cyril G. Hopkins (33) and his associates of the Illi- 
nois Experiment Station presented at the nineteenth annual meeting of the 
Association of Official Agricultural Chemists the first practical method for 
ascertaining quantitatively the acidity or lime requirements of a soil. The 
method is based on the theory that the acids, organic and mineral, in the soil 
are insoluble in water and cannot be extracted with water, but when a mineral 
salt solution is added to the acid soil, a double decomposition takes place, 
the acids (humic acids) react with the salt solution, uniting with the mineral 
base, forming neutral humates and liberating the mineral acid or an acid salt. 
The titration of the mineral acid serves as a basis for determining the total 
acidity of the soil. Eichhorn (16) found that soil rich in humus and contain- 
ing free humic acids, liberates the acid from neutral salt solutions when brought 
in contact with such a soil. Solenow (64) also observed that the difficultly 
soluble organic acids of the humus liberate mineral acids which may affect 
the plants growing on the soil affected. These observations are at variance 
with that made by Knop and Detmer (69) who claim that generally '"humates" 
and ''humic acids" are much less soluble in salt solutions than in pure water. 
But Heiden and Schumacker (37) demonstrated that portions of salts in solu- 
tion are removed by peat, prepared humic acids, and artificial humus when 
these come in contact with the salt solution. Veitch (80) is also of the opinion 
"that organic matter is able to remove from solution a portion of the mineral 
salt with which it is brought in contact," but further asserts that "none of 
the standard works on absorption of soils makes mention of the production 
of free mineral acids; neither theoretical considerations nor a cursory examina- 
tion of the literature lead one to believe that mineral acids in amounts equiv- 
alent to the total organic acids are set free by the action of mineral salt solu- 
tions on acid organic material." 

Shortly after the publication of the Hopkins method of soil acidity-deter- 
minations, Veitch (80) subjected it to a critical study. Tests were made for 
free hydrochloric acid in the extract, and except in one or two cases where 
the presence of water-soluble sulfuric acid was proven, there were no tests 
which showed a considerable amount of free acid. Tests for phosphoric acid 
gave a negative result. In a previous work on the solubility of soil ingredient 

153 

BOIL SCIENCE, VOL. X, NO. 3 



154 JOSE JISON IHEASOL 

in saline solutions, \'eitch, however, noted the filtrates were frequently acid in 
reaction, and attributed it to the presence, in considerable quantities, of alumi- 
num, iron and manganese in the solution. He further found that when the 
apparent acidity of the extract was equivalent to more than 1 or 2 cc. 0.05 N 
alkali a precipitate was formed on titration which he identified as the hydrox- 
ides of aluminum, iron and manganese. Ames and Schollenberger (3) by 
experiment undertook to demonstrate that free acid is formed by interchange, 
between acid soils and potassium nitrate solution. The procedure is described 
in Bulletin 306 of the Ohio Agricultural Experiment Station. The results 
obtained from 200 cc. of the potassium nitrate extracts are the following: 

Acidity due to free acid, by titration with methyl orange 9. 1 cc. 0.1 -V NaOH 

Total acidity to phenolphthalein 39.9 cc. 0.1 N NaOH 

Acidity due to salts of Fe and Al (by difference) 24.8 cc. 0.1 iV NaOH 

Chlorine equivalent to 0.3 cc. 0.1 N AgNOs 0.0476 gm. 

Silica, by loss after HF treatment 0.0005 gm. 

Ferric .and aluminum oxides .0471 gm. 

Iron by reduction and titration as FesOa 0.0136 gm. 

AI2O3 by difference 0.0335 gm. 

The iron was found equivalent to 5.0 cc. of 0.1 .V NaOH; and the alumina to 19.7 cc. 

It is thus seen that although free acid has developed the acidity due to the 
presence of aluminum is more than twice the acidity due to free acid. The 
following opinion by Veitch (80) fits well with tliis result a.s well as with his 
own: "It seems that there is no setting free of appreciable quantities of hy- 
drocliloric acid, and that there is practically no reaction between the organic 
matter and the salt solution, whereby difficultly soluble organic acids are dis- 
solved, but that the acidity of the filtrate (or the acidity wliich is greater than 
would be given by water under the same condition) is due to the solution of 
alumina or some other acid-salt yielding base." 

The author has also made some studies on the composition of potassium 
nitrate extracts of three acid soils. A more detailed account of the results of 
this study will be given in the latter part of this paper, but the conclusion he 
reached is that potassium nitrate solution brings into solution the aluminum 
in the acid soil when the latter is brought in contact with the salt solution; 
that the strong acidity exhibited by the potassium nitrate extract is due largely 
to the presence of a considerable amount of aluminum in solution; and that 
the precipitate formed at the point when the extract passed from an acid into 
an alkaline solution is largely aluminum hydroxide. 

Hitherto, the significance of Veitch's discovery has never been appreciated, 
and the nature of soil acidity has generally been ascribed to the presence of 
free organic and mineral acids in the soil. The recent work, however, of such 
men as Abbott, Conner and Smalley (1) of Indiana, Ruprecht and Morse of 
Massachusetts (59) and Hartwell and Pember (27) of Rhode Island, in which 
the}- have shown the role aluminum j)lays in some acid soils, has given a new 
phase to the prol)lcm of soil acidity. The last two men, especially, are so 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 155 

convinced of the presence of aluminum in acid soils as the cause of the differ- 
ent behavior of barley and rye grown in an acid soil that they think "the 
elimination of the effect of aluminum in acid soOs seems likely to prove more 
important than the neutralization of the acidity" and that "attention should 
be given to methods of determining active aluminum while we are also devel- 
oping those for soil acidity" (28). If aluminum should prove to be the most 
important factor in acid soils, and a search is made for a method for deter- 
mining active aluminum and for eliminating its effect in acid soils, such a 
method already exists. Veitch had demonstrated that the Hopkins method 
does not bring considerable free acids in an acid soil into solution but instead 
brings the aluminum in the soil into solution; the apphcation of the method 
to field conditions has brought excellent results. In other words, the method 
determines aluminum. The application of limestone to acid soils, according 
to the method, eliminates the effect of aluminum, and so far as aluminum is 
concerned in acid soils the Hopkins method is the best method for determining 
and correcting soil acidity. 

n. OPINIONS CONCERNING THE CAUSE AND NATURE OF SOIL ACIDITY 

Frear (19) and Ames and SchoUenberger (3) have already reviewed quite 
comprehensively the literature and theories covering the subject of soil acidity 
and in this paper the author only attempts to summarize briefly the opinions 
expressed by the different investigators. These opinions or theories may be 
divided into three groups. 

1. The presence of true acids. 

2. Adsorption by soils. 

3. The presence of considerable quantities of soluble aluminum salts. 

1. The presence of true acids 

In this group there are two important theories, the organic acid theory and 
the mineral acid concept. Let us take up first the organic acid theory. 

In the decomposition of plant and animal residues organic acids are pro- 
duced. Under proper aeration these decomposition products are used up by 
soil organisms as fast as they are formed. But in poorly aerated and drained 
soils, these products may accumulate giving rise to acid condition. The acidity 
of some peat and muck soils has long been known, and this acidity has been 
assigned to complex insoluble organic acids. This theory was proposed by 
Sprengel (65) after having discovered what he called humic acid. Berzelius 
(6) further advanced the theory when, by treating a soil with an acid he ob- 
tained two substances, one insoluble and the other soluble, the latter being 
identical to the huniic acid of Sprengel. Tacke and Slichting (71) held the 
view that the acidity of humic acids can only be accounted for on the basis of 
true acids. That organic acids exist in normal soils is a known fact. Blair 
and Macy (8) in Florida found muck soils which gave an acid aqueous extract 



156 JOSE JISON iURASOL 

after boiling the extract for a long time. They ascribed the acidity to soluble 
organic acids in the soil. The so-called humus has been subjected to a critical 
examination by Shorey (63) who found thus far at least thirteen organic acids, 
among which are oxalic acid, succinic acid, saccharic acid, acrylic acid, picoline 
carboxylic acid, paraffinic acid and lagnoceric acid. But it is believed that 
under ordinary conditions the organic substances present in the soil cannot 
bring a condition unfavorable to plant growth. 

Some soils while deficient in organic matter are decidedly acid, hence it 
follows that the acidity in this case must be attributed to other causes. Truog 
(75) thought that the acidity in this case is caused by true acids. It is claimed 
that plants and certain hydrated compounds in the soil removed the bases 
from the salts leaving free acids. Stoddart (67) for example, is of the opinion 
that the sulfates and chlorides in the soil are split up, the base elements being 
absorbed by the plants, leaving the acid radicals as acids thus giving rise to 
an acid condition. It is further believed that the silicates which are import- 
ant constituents of soils of non-limestone rock origin are decomposed by car- 
bonated water in the soil resulting in the removal of bases which are either 
taken up by plants or leached out. The oxides of silicon and aluminum 
left over combine to form aluminum-silicic acids which may cause soil acidity. 
Truog (77) says: "It is possible that mere removal of bases from the original 
silicates may give rise to acid silicates which cause soil acidity." On this 
point Hopkins (32, p. 176) says, "Acid silicate is formed from polysilicates 
from which some basic elements may have been removed and replaced with 
acid hydrogen, by reaction with soluble organic acids, or possibly by the long- 
continued weak action of drainage waters charged with carbonic acid, do e.xist 
in the soil, and the evidence thus far secured indicates that they account for 
most of the acidity of soils which are at the same time strongly acid and very 
deficient in humus." In the study of acid red clay soils of Porto Rico, Loew 
(41) ascribes the acidity to the presence in the soils of an acid clay or aluminum 
silicates having the formula H4Al2Si209, which he called argillic acid. 

Lastly by the use of electrometric and colorimetric methods of determining 
hydrogen-ion concentration, Gillespie (22) demonstrated the presence of acid 
in the soil. His findings were in accordance with the results of Sharp and 
HoagLnd (62), who concluded that soil acidity is due to the presence of an 
excess of hydrogen ions in the soil solution. 

It is believed that certain treatments of the soil may also give rise to acidity 
in the soil. Continued application, for example, of artificial fertilizers like 
sulfate of ammonia and acid phosphate causes acidity of the soil. When sul- 
fate of ammonia is applied to soils, ammonia is nitrified leaving the sulfate 
radical to form sulfuric acid. Muriate of potash, according to Stoddart (67) 
tends to leave an acid residue due to the absorption of potassium by plants or 
soil colloids, leaving free sulfuric and hydrochloric acids. There are instances 
in which continued application of ammonium sulfate to the soil resulted in 
an acid soil. Wheeler (82) reported acid the soil in the plots of the Rhode 



ALUiVaNUM AS A FACTOR IN SOIL ACIDITY 157 

Island Experiment Station which received ammonium sulfate continuously. 
Hall and Gimingham (24) in England, Hunt (35) in Pennsylvania and Ru- 
precht and Morse (60) in Massachusetts encountered similar results with ex- 
perimental plots receiving ammonium sulfate continuously but not limed. 

It has also been thought that acid phosphate may produce acidity in the 
soil. The fact that acid phosphate is an acid salt is responsible for this belief. 
In discussing the advantages of raw phosphate over acidulated phosphate 
Hopkins (32, p. 242) says: "A third point in favor of raw phosphate in com- 
mon with bonemeal and slag, is that it is free from acidity and has no tendency 
to injure the soil. This is a minor advantage, because if acidity develops from 
the use of acid phosphate (and it does) it can be corrected at a small expense 
by the addition of any form of lime." Thorne (72) of the Ohio Experiment 
Station also is of the opinion that acid phosphate may develop acidity in the 
soil. He says: "There is reason to believe that acid phosphate increases the 
tendency to soil acidity, but it is not the sole cause of such acidity for there 
are very acid soils which have never received any phosphate." These opinions, 
however, do not agree with the experimental evidence. In a study of the 
acidity of experimental plots in Indiana in which acid phosphate has been ap- 
plied for twenty years, Conner (13) found that these plots show less acidity 
than soils which have never had acid phosphate. By computing the amount 
of free phosphoric acid added to the soil when the rate of appHcation is 200 
pounds of acid phosphate containing 14 per cent available phosphoric acid, 
Frear (19) concluded that it would take a long time and a large amount of 
phosphate to make a soil acid by such direct action. The results of the au- 
thor's tests which will be presented in this paper also indicate that acid phos- 
phate tends to reduce rather than increase the acidity of the soil. 

Z. The adsorption theory of soil acidity 

The phenomenon of soil acidity has also been explained as a case of adsorp- 
tion. Cameron (11) was the first to apply the theory of adsorption in explain- 
ing the acid reaction of certain soils. He attacked the blue Htmus paper test 
for soil acidity on the ground that wet cotton also turns blue litmus paper red. 
He is of the opinion that the reddening of blue litmus paper by certain soils is 
a case of selective adsorption. 

After investigating some acid soils of Michigan, Harris (25, 26) arrived at 
the conclusion that the acid reaction of the soil is due to selective adsorption 
and not to the presence of acids. 

Parker (49) asserts that because of the nature of the surface of its constitu- 
ents soils adsorb the cation at a greater rate than the anion, and that the 
acid reaction of certain soils is due to this fact. 

In a comprehensive study of acid soils of Japan, Daikuhara (14) concludes 
that their acid reaction is not due to organic acids (humus) alone but also to 
adsorption of coUoidal compounds of aluminum and iron. 

Gully (23) also ascribes the acid reaction of peat moss and peat soils to 
adsorption of the colloidal matter of the covering of the sphagnum cells. 



158 JOSE JISON MIRASOL 

3. The presence of soluble salts of aluminum in the soil 

The idea had its inception in the work of Abbott, Conner, and Smaller (1) 
who investigated a few years ago, the causes of the unproductivity of some 
soUs in Indiana. They obtained water extract of the acids soils, and deter- 
mined its composition. They have found that the extract reacts acid to phe- 
nolphthalein and that the nitrate was present partly as aluminum nitrate. 
Corn seedlings were grown in the extract along side of solutions of nitric acid 
and aluminum nitrate of known normality, and it was found that the extract 
was extremely toxic up to 0.0005 N . It was found that the toxicity of the ex- 
tract was equal to the to.xicity of nitric acid and aluminum nitrate of the same 
normality; and the conclusion arrived at was that soluble salts of aluminum 
are largely responsible for the unproductiveness of the soils in question. 

Ruprecht and Morse (60), investigating the effect of continued application 
of ammonium sulfate to soils, found that aluminum sulfate is formed which 
causes the acid reaction and the unproducti\ity of the soil. 

Hartwell and Pember (27) carried on a comprehensive search for the cause 
of the different behaviour of rye and barley grown on soils from plots continu- 
ously receiving ammonium sulfate. Different inorganic substances have been 
subjected to experiment to discover the most active factor and the conclusion 
reached was that aluminum is the element responsible for the depression of 
the growth of barley. 

After reviewing the different theories concerning the nature and cause of 
soil acidity Ames and Schollenberger (3) expressed the following opinion: 
" The theory of the existence of silicic or alumina-silicic acids in the soil would 
serve as a complete explanation for all the observed phenomena; the concep- 
tion is simple and is supported by analogy with bettter known reactions which 
is as much as can be said for any of the theories which have been offered." 

The work of Abbott, Conner and Smalley, Ruprecht and Morse, and of 
Hartwell and Pember, however, has opened up new possibiUties by which the 
nature and causes of soil acidity could be studied further. With the hope that 
more light might be thrown upon aluminum as a factor in soil acidity the pres- 
ent work has been undertaken, bearing in mind three facts. First, aluminum 
salts are highly toxic at a certain concentration; second, aluminum is abund- 
ant in the soil, being next to oxygen and silicon; and third, plants absorb bases 
and calcium carbonate is leached out of the soil resulting in the depletion of 
the soil of this compound and enabling the aluminum in the soil to act as a 
base. 

III. ALUMINUM IN AGRICULTURE 

Aluminum is universally known as a non-essential element to plants. Hy- 
drated silicates and oxides of aluminum, however, are believed to exercise 
great influence in holding some of the i)lant-food elements in the soil, prevent- 
ing their loss in drainage water. Aside from this, aluminum has no economic 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 159 

value in agriculture. As stimulants or as fertilizers very little is known of 
aluminum compounds and the few scattered experiments on this subject are 
incomplete and inconclusive. On the other hand, aluminum has been found 
extremely to.xic to plants. Since aluminum is abundant in the soil and under 
certain conditions becomes harmful to plants, as in the case of some acid soils, 
it is in this fact that aluminum will prove of great importance to the agricul- 
turist. 

Aluminum in plants 

Although aluminum is not an essential element, analyses of ashes show that 
it is taken up by plants. It is, however, present in small amounts in most 
plants. Pfeffer (50) speaks of the abundance of aluminum in Lycopodiiim 
chamaecyparissiis and L. alpinum, where it constitutes from 22 to 27 per cent 
of the ash, while in certain species of Lycopodiiim only traces are found. John- 
son (37) states that aluminum is found in small amounts in the ashes of agri- 
cultural plants, but added that it is not clear whether it is an ingredient of the 
plants or due to particles of clay adhering to plants. Robinson, Steinkoenig 
and Miller (57) report analyses of legumes, vetetables, grasses, trees, shrubs, 
and show that aluminum is found in all the plants analyzed. The form in 
which aluminum is present in the plant is not known. According to Berzelius, 
aluminum as alumina is united with tartaric acid, and according the Ritthausen 
with malic acid [quoted by Johnson (37)]. Pfeffer (50), however, is not certain 
whether aluminum in Lycopodium is present in the form of tartrate. In a 
study of the aluminum contents of certain vegetables including corn and corn 
products, hominy, oatmeal, carrots and white and sweet potatoes, Meyers 
(44) found that aluminum in these vegetables is found in a soluble form, and 
averred that a relatively large consumption of aluminum may result from a 
diet consisting chiefly of vegetables. 

Physiological action of aluminum on plants. According to Jost (38) Jamano 
found aluminum to be of service in the development of barley. This is in 
conflict with the results of Hartwell and Pember (27), in which they show that 
the depression of the growth of barley in an acid soil is due to the presence of 
aluminum. Maze (43) also asserts that aluminum is necessary for the best 
growth of maize. E.xperimental evidences, however, point to the fact that 
aluminum is not only a non-essential element but it is also very harmful to 
plants under certain conditions. 

Fluri (18) describes certain experiments carried out on Spirogyra, Elodea, 
and Lemara with sulfate, nitrate, chlorate and bichromate of aluminum. He 
found that in light, production of starch is reduced, but also found that while 
assimilation was checked it was not inhibited. The aluminum found in the 
cell was small and the action could not then be attributed to a chemical reac- 
tion. But as starch production was affected it was thought that the action of 
aluminum was on the diastase. 

Hebert (29) made some germination tests of peas, wheat and rape with 
sulfates of aluminum and other metals and found that the salts were strongly 



160 JOSE JISOX MIRASOL 

poisonous. \'arvaro (79) also reports that aluminum oxide, like the oxides of 
manganese, iron, uranium, cerium, copper, zinc, cadmium, mercury and lead 
has a retarding efltect on the germination of kidney beans, but has an accelerat- 
ing effect in the case of corn. Experimenting on the effect of dififerent alumi- 
num salts on the germination of wheat, Micheels and DeHeen (45) found that 
while kaloin and alumina were somewhat beneficial, the salts were very 
harmful. 

In investigating the effect of different sails of aluminum on the growth of 
Zea mays, Vicia faba, Lens esculenta and Helianlhus anmiiis Kratzmami (30) 
found that the growth was hindered by the salts when the concentration was 
0.005 per cent, but stimulated when the concentration was only 0.0001 per cent. 
Aluminum nitrate showed a toxic effect. In tliis connection, significant is the 
statement of House and Gies (35) that the toxicity of aluminum salts depends 
upon the concentration of the solution. Yamano (84) found that moderate 
amounts of aluminum salts have a stimulating effect upon the development of 
barley and flax. He further found that in water culture 0.2 per cent of alum 
proved injurious after three weeks while 0.8 per cent killed the plant in a few 
days. Miyake (46) also found that the aluminum chloride is toxic even in 
dilute solution. The toxicity appeared when the concentration was greater 
than 0.000133. It was further found that the toxicity of aluminum chloride 
was approximately equal to that of hydrochloric acid of the same normality. 
Under the supervision of Professor C. F. Hottes of the Department of Plant 
Physiology, the author carried on some experiments on the toxicity of alumi- 
num sulfate to barley. Solutions of 0.01 N, 0.001 N, 0.0001 N, and 0.00005 
A^ were prepared, and barley seedlings were grown in them. The author 
found that the average growth of 10 plants for 7 days was 70.5 mm. in the 
control; 45.5 mm. in 0.01 .V; 65 mm. in 0.001 N; 71.5 mm. in 0.0001 X and 78.9 
mm. in 0.00005 N. It is thus seen that 0.01 .Y is highly to.xic; 0.001 Y depresses 
growth; and 0.0001 Y has no effect at all. In 0.00005 Y stimulating effect 
was noted. It was further observed that the seedlings growing the first two 
dilutions had root systems more than three times as greatly depressed as those 
growing in the control or in any of the two weaker solutions. The limit of 
toxicity lies probably between 0.0001 Y and 0.001 Y. 

Other investigators who have proved the toxicity of aluminum salts are 
Abbott, Conner and Smalley; Ruprecht and Morse; and Hartwell and Pember, 
whose works have been already mentioned in the preceding discussion. It may 
be said, however, that it was not until the work of these men appeared that 
the to.xicity of aluminum salts has been linked with the soil as a contributing 
factor in soil acidity. 

Aluminum salts as slimulanls and fertilizers 

Experiments have been made to ascertain the value of aluminum salts as 
catalyzers or stimulants. Pfeiffer and Blanck (51) found that small amounts 
of aluminum sulfate combined with a small portion of manganese sulfate 



ALVMINUM AS A FACTOR IN SOIL ACIDITY 161 

caused an increase in the yield of dry substance in the grain, but an increase 
of the salt reduced the yield. Stoklasa (68) reports results from experi- 
ments on catalytic fertilizers for sugar beets. He showed that a combined 
appHcation of 9 kgm. (19.8 lbs.) of manganese and 4.48 kgm. (9.8 lbs.) of 
aluminum sulfate per hectare has increased the j'ield of sugar beets from 30 to 
50 per cent. He is of the opinion that aluminum, like manganese, zinc, and 
copper, is a catalytic agent, performing a function in the assimilation of car- 
bon by promoting rapid photosynthesis. Boullanger (9) made a comparative 
study of the catalytic value of the sulfates of aluminum, manganese, ferrous iron 
and uranium, and found that while the results obtained were not uniform, in 
the majority of cases they increased the yield. In the case of aluminum ni- 
trate, however, the experience of Munerate, Mezzadroli and Zapparole (47) 
was different. They carried on a comparative test of the stimulating value 
of aluminum nitrate and sulfate together with the sulfate, chloride, dioxide 
and carbonate of manganese, boric acid, borate of soda and sulfate of uranium. 
The results showed that the lowest yield of sugar beets was obtained in the 
plot which received 100 kgm. (220 lbs.) per hectare of aluminum nitrate. 

An attempt has been made also to find the effect on the productivity of the 
soil by the application of aluminum silicates. Voelcker (81) reports pot cul- 
ture experiments in which green manures were associated with aluminum sili- 
cates, sodium silicates, kaolin, lime and magnesia. The results obtained 
showed that kaolin did not increase the yield of crops, but aluminum silicates 
with mustard as a green manure caused a large increase in the crop. 

Finally, experiments have been carried out to determine the value of in- 
soluble aluminum phosphate as a source of phosphorus to the plants. Pri- 
anishnikov (52) describes sand culture experiments in which wheat, oats, bar- 
ley, peas and buckwheat were fertilized with aluminum phosphate alone and 
with calcium carbonate. The conclusion reached was that aluminum phos- 
phate is assimilated, and that calcium carbonate had no appreciable depressing 
efltect on the assimilability of aluminum phosphate. Baguley (4) reports a 
comparative test of orthophosphates of iron, calcium and aluminum on oats, 
peas and Swedish turnips grown on sand and chalk. The results obtained 
were better with iron and aluminum phosphates than with calcium phosphate. 
Truog (74) also presents results of experiments carried out in the greenhouse 
\vith ten different kinds of plants manured with rock phosphate, precipitated 
calcium phosphate, and phosphate of aluminum, iron and manganese. The 
results obtained were summarized as follows: "Contrary to the general belief 
that aluminum and iron phosphates are relatively unavailable to plants, nine 
of the ten plants tested made better growth on aluminum phosphate than on 
calcium phosphate, and six better growth on iron (ferric) phosphate." In 
another publication (76) in which results from a more comprehensive series of 
experiments on phosphate involving a large number of plants, were presented, 
he draws this conclusion: "Precipitated ferric and aluminum phosphates pro- 
duced with a few exceptions good growth and in a few cases e\'en better growth 
than the acid phosphate." 



162 



JOSE JISON MIRASOL 



Aluminum in the soil 

Aluminum is the most widely scattered metal (53) and next to oxygen and 
silicon is the most abundant element. It constitutes 7.85 per cent of the litho- 
sphere and 7.30 per cent of the lithosphere and atmosphere combined (12). It 
does not occur in nature in the free state, but in combination with o.xygen, the 
alkalies, flourine, sihcon, the acids, etc., it forms minerals and rocks which 
on disintegration become the bases of soils and clays. Aluminum is present in 
the soil as the oxide, hydroxide, hydrated oxides, phosphate and silicates (64'). 
In order to giv'e some idea as to the amount of aluminum present in the soil, 
analyses of some soils in .\merica are given in table 1 . 



CONSTITDENTS 



SiOj 

AW, 

Fj03 

MnO 

MgO 

CaO 

NajO 

K,0 

HjO 

P2O6 

COj 

Organic matter. . 

SO, 

CI 

Loss on ignition . 







TABLE 2 










Chemical analyses of some A merican soils 














LIME- 










""■»' 


SOILS 


COASTAL 

PLAras 

PROVTKCE 


STONE 
VALLEY 

AND 
UPLAND 
PROVINCE 


PIED- 

UONT 

PLATEAD 

PROVINCE 


GEZAT 
PLAINS 
PROVINCE 


GLACIAL 

AND 
LOESSIAL 
PROVINCE 


FLOOD 
PLAIN? 
PROVINCE 


A 


B 


No. 1 


No. 3 


No. 15 


(1) 


(5) 


(13) 


per cent 


per cent 


per cent 


per cent 


per cent 


per cent 


per cent 


Per cent 


19.24 


66.69 


94.50 


79.25 


66.49 


78.85 


76.81 


93.29 


3.26 


14.16 


2.07 


8.89 


17.11 


9.68 


9.73 


2.45 


1.09 


4.38 


0.83 


4.44 


7.43 


2.72 


3.26 


0.78 


Trace 


0.09 


0.007 


0.07 


0.51 


0.036 


0.068 


0.066 


2.75 


1.28 


0.09 


0.33 


0.31 


0.72 


0.60 


0.01 


38.94 


2.49 


0.39 


0.63 


0.36 


0.94 


0.92 


0.15 


Trace 


0.67 


0.11 


0.24 


0.16 


2.02 


1.74 


0.03 


Trace 


1.21 


0.10 


0.67 


0.62 


2.31 


2 20 


0.45 


1.67 


4.94 














0.23 


0.29 


0.06 


0.18 


0.17 


0.11 


0.12 


06 


29.57 


0.77 














2.96 


2.00 


1.13 


1.96 


1.26 








0.53 


0.41 


0.07 


0.13 


0.07 


0.07 


0.11 


0.10 


0.11 


0.34 


















1.74 


4.80 


8.06 


2.28 


4.09 


2.12 



The first two columns are adopted from Clarke (12), the next three from Rob- 
inson (55) and the last three from Robinson, Steinkoenig and Fry (56). The 
soil indicated A, is from Salt Lake City, Utah; B is from Santa Fe, New Mexi- 
ico; No. 1 is Norfolk sandy loam, 3 miles southwest of Laurinburg, North 
CaroUna, depth to 14 inches; No. 2 is Decatur clay loam, 1 mile east of Holly- 
wood, Alabama, depth to 4 inches; No. 15 is Cecil clay 2\ miles northwest of 
Charlotte, North Carolina, depth to 6 inches; (1) is Colorado sand near Gree- 
ley, Colorado, depth to 14 inches; (5) is Knox silt loam, 2 miles north of Far- 
ley, Missouri, depth to 14 inches; and (13) is Cahaba very fine sandy loam, 
Minden, Louisiana, depth to 12 inches. For further details about these 
soils the reader is referred to the publications of these men. 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 



163 



By recalculation the total aluminum in these soils per acre of 2,000,000 
pounds of surface soil amounts to 34,576 pounds for Salt Lake City adobe; 
151,181 pounds for Santa Fe adobe; 21,954 pounds for Norfolk sandy loam. 
North Carolina ; 94,237 pounds for Decatur clay loam, Alabama ; 1 8 1 ,469 pounds 
for Cecil clay, North Carolina; 102,666 pounds for Colorado sand; 103,196 
pounds for Knox silt loam, Missouri; and 25,985 pounds for Cahaba very fine 
sandy loam, Louisiana. 

Burd (10) also reports total analyses of certain silty clay loam and fine sandy 
loam soils in California in wMch, for example, one silty loam soil and one fine 
sandy loam soil contain 14.03 per cent and 16.73 per cent alumina, or 148,802 
pounds and 177,438 pounds aluminum per acre, respectively. 

Aluminum in the subsoil. Analyses of the subsoils of soils given in the pre- 
ceding table show larger quantities of aluminum. For example, the subsoil 
of Decatur clay loam contains 3 per cent more alumina than the surface soil. 
In every one of the ten subsoils analyzed by Robinson (55) alumina is higher 
than in the surface. 

TABLE 2 
Alumina in soil separates 



SEPARATES 


HEAVY LOAM 


LOAMY LOESS 

son. 


COARSE SANDY 

GNEISS son. 


Coarse dust, 0.25 to 0.01 mm 

Medium dust, 0.01 to 0.005 mm 

Fine dust, 0.005 to 0.0015 mm 

"Clay" (Schlamm), 0.0015 to mm 


percent 

1.63 
15.20 
20.48 
27.76 


percent 

7.28 
14.20 
19.41 
29.97 


percent 

18.71 
24.20 
30.21 
32.42 



Distribution of aluminum in the soil separates. There have been a few at- 
tempts to determine the distribution of the chemical constituents of the soil 
in the different soil separates. Puchner, quoted by Failyer, Smith and Wade 
(17), presents data of chemical analyses for separates of three types of soil. 
The percentage of alumina found is given in table 2. 

Steinkoenig (66) also reports determination of certain constituents of sepa- 
rates of ten loam soils from New York, North Carolina, Pennsylvania, South 
Carolina, Virginia, New Hampshire and Wisconsin. The average alumina 
found in the separates of these soils, together with the maximum and minimum 
is given below: 





FINE SAND 


COARSE SILT 


FINE SILT AND 
FINE CLAV 


Average 


per cent 

5.48 
12.56 
0.40 


per cent 
8.44 

18.28 
1.48 


Per cent 

22.57 
31.33 




16.76 







164 JOSE JISON MIRASOL 

From the data above it can be seen thai the largest quantity of aluminum 
is found in the finest particles of the soil and that the quantity diminishes as 
the particles become coarser. It follows from this fact that the more clayey 
the soil is the higher is the aluminum content, and this seems to be the case if 
the Cecil clay is taken as proof. 

The aluminum compound in the soil thai gives rise to soluble aluminum salts. 
Mention has been made before that aluminum is present in the soil as oxide, 
hydrated o.xides, hydroxides, phosphates and silicates. But which of these 
compounds breaks up so readily in the soil to form soluble salts that proved 
injurious to crops in some soils, as has been found by Abbott, Conner and Smal- 
ley, and Ruprecht and Morse? We naturally look upon hydro.xides. There 
are three forms of aluminum hydroxides recognized: Diaspore — AI2O3H2O, 
bauxite — AL03-2H20, and gibbsite, otherwise called hydrar-giOite or oxyhy- 
drates, A1203-3H20 (53). Do these three forms behave chemically the same with 
mineral acids? Diaspore and bauxite are insoluble in cold and hot water and 
in acids and alkalies, but gibbsite, while not soluble in cold and hot water, is 
soluble in acid and alkalies (48). Moreover, the so-called aluminum salts, 
aluminum nitrate, Al206(N02)6, aluminum acetate, Al206(C2H30)6, aluminum 
sulfates, Al206(S02)3, and aluminum phosphate Al206(P04)2 — are chemically 
considered as derivatives of the oxyhydrates (53). Gibbsite, therefore, an- 
swers the first question, and the next question that comes up is, whether 
gibbsite is present in the soils of ^^merica. 

Laterilizalion in northern climates. In the decomposition of rocks an insolu- 
ble residue made up mainly of silica, alumina and ferric oxide, and combined 
with water, is left over. When kaolinite is the predominant constituent of the 
residue it is called clay, but when hydrates of alumina and iron predominate the 
residue is called laterite. Hence, the process of rock decomposition in which 
kaolinite is the end product is called kaolinization and that process in which 
hydrates of alumina and limonite are the ultimate products is called lateritiza- 
tion (15). In regard to the latter process Clarke (12) says, "In the tropical 
and subtropical regions the processes of rock decay are often carried further 
than is usually the case within the temperate zones. The leaching is more 
complete, the silicates are more thoroughly decomposed, and the residues are 
richer in hydroxides." 

Ther; is a general opinion among geologists that kaolinization is character- 
istic of rock decomposition in northern climates while lateritization is charac- 
teristic of that in tropical and subtropical regions. For this reason there is a 
diversity of opinion as to the occurrence of aluminum hydrates in the soils of 
America. Cameron and Bell (11) for example, state that "either gibbsite or 
bauxite is but seldom found in soil," and that in the examination of several 
thousand soils from all over the United States, in only one soil, that which 
comes from southern California, was aluminum hydroxide observed. Lind- 
gren (40) is also of the opinion that little or no aluminum hydroxide is formed 
in ordinarv rock weathering, and that the occurrence of bauxite is a raritv in 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 165 

the temperate climate. On the other hand, Edwards (15) by recalculating 
analytical data for clays from different states, shows that bauxite exists in 21 
states besides those in which the mineral exists in deposits of commercial value. 
In regard to the independence of bauxite as a mineral species Lindgren (40) 
says, "The independence of bauxite as a mineral species, is, however, ques- 
tioned and it is believed rather to be a mixture of diaspore and gibbsite. The 
Georgia bauxite according to T. L. Watson corresponds well to gibbsite." 
Hilgard (30) found a high ratio of alumina to soluble silica in some of the soils 
he examined, and could not attribute it to other than the presence of hydrous 
alumina, possibly gibbsite. Beyer and Williams (7) reporting the analyses of 
flint fire clays from Missouri and New Jersey, also found a higher ratio of alum- 
ina to silica than that found in kaolinite but attributed it to the presence of a 
more highly aluminous silicate which he called pholerite. In the reported anal- 
yses of ball and flint clays from Missouri and of fire clays from Pennsylvania, 
Rolfe (58), again, found a high proportion of alumina to silica, and attributed 
this to the presence in the clays of gibbsite or other minerals high in alumina. 
Ries (54) believes that there is the possibility that in kaolins high in aluminum 
bauxite or gibbsite might be present. Finally, Galpin (21) in the study of 
flint clays and their associates encountered highly aluminous fire clays from 
near St. Louis, Missouri, and proves that the excess of alumina to silica is due 
to the presence of gibbsite. 

The author does not pretend to show that aluminum hydrates are of common 
occurrence in the soils in America, but with the evidence gathered from the 
works of the men mentioned above he can not help reaching the conclusion that 
in some soils in the United States hydrates of alumina are present, and that 
in the case of soils where sufficient amounts of soluble salts of aluminum are 
found to be harmful to crops, the aluminum compound furnishing the alumi- 
num is gibbsite, and until further investigations prove the contrary the author 
will hold to this view. 

IV. EXPERIMENTAL 

The problem 

The work reported in this paper has been undertaken with the view of gain- 
ing some information on the following questions: 

1. Aluminum is found in the soil in abundance and in conditions of varying 
stability. When an acid soil is extracted with potassium nitrate solution 
aluminum is brought into solution and is largely responsible for the acid reac- 
tion of the extract. Is not the acidity of the so-called acid soil due to the 
presence of active aluminum in the soil? 

2. Sweet clover does not grow on a strongly acid soil while other plants have 
their growth depressed. Since aluminum salts have been found highly toxic 
even in dilute solutions, is not this behavior a reaction to the toxicity of soluble 
salts of aluminum in the soil? 



166 JOSE JISON MIRASOL 

3. When acid soils are treated with limestone according to the potassium 
nitrate method, sweet clover thrives well. Does not calcium carbonate elim- 
inate the toxicity of aluminum? And if so, how does it act? 

4. Does acid phosphate increase the acidity of an acid soil? 

5. If the acidity of the soil is due to the presence of active aluminum, what 
effects have soluble salts of aluminum on sweet clover growTi in sand? What 
effect has aluminum salts on sweet clover in the presence of calcium carbonate, 
or acid phosphate? 

General plan of the work 

Based on the foregoing propositions, plans have been carried out: 

1. To study the potassium nitrate extract of an acid soil before and after 
the application of limestone. 

2. (a) To leach out a considerable quantity of acid soils with potassium ni- 
trate and with water until the last 125 cc. of leachings no longer indicate acid- 
ity, and to grow crops on it. 

(b) To analyze the leached out soils for aluminum, iron and manganese. 

3. (a) To grow crops on acid soils, treated with limestone and acid phos- 
phate, alone and in combination with each other, and in different amounts. 

(b) To set aside a similar series as above, giving the same treatment 
except the growing of crops, for acidity determinations in two different periods. 

4. To grow crops on sand treated with aluminum sulfate, aluminum chlor- 
ide and aluminum nitrate and aluminum hydro.xide, alone and in combination 
with calcium carbonate or with acid phosphate. 

Description of tin- material used 

Three types of soil have been secured from southern Illinois for this work. 
They are — gray silt loam, on tight clay of the lower Illinoisan glaciation area; 
yellow gray silt loam, an upland timber soil; and yellow silt loam from the 
unglaciated areas. All the soils were acid to the blue Utmus paper test. The 
phj'sical composition of these soils is given in table 3. The Bureau of Soil's 
method and grades of mechanical separation have been adopted in this analy- 
sis (42). Some of the chemical constituents of the soils are given also in col- 
umn 2, table 4. Except for aluminum, iron and manganese, the methods of 
chemical analysis used were those of the University of Illinois Agricultural 
Experiment Station. Aluminum, iron and manganese were determined by a 
combination of some of Hillebrand's procedures and of some in Treadwell's 
"Qualitative Analyses." The sample was fused with sodium bicarbonate, 
and the subsequent steps as directed in Hillebrand's methods, were followed 
up to the point of precipitating aluminum and iron. The ammonium pcrsul- 
fate method was adopted at this point to precipitate the manganese together 
with aluminum and iron (31). Manganese was then separated from aluminum 
and iron by the barium carbonate method and determined as manganese 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 



167 



pyrophosphate as directed in Treadwell's process (73). Aluminum was sepa- 
rated from iron by the potassium hydroxide procedure and both were weighed 
as oxides, also according to the direction of Treadwell. 

Gray silt loam. This is a surface soil taken from the border of one of the 
control plots of the experimental fields at Newton, Jasper County. It con- 
tains 98.24 per cent dry matter. The reaction as tested in the laboratory is 
acid, and the acidity or lime requirements according to the Hopkins method 
is 2125 pounds of limestone of 93 per cent purity, per acre (2,000,000 pounds 
of soil 6f inches). The amounts of essential plant-food elements found are: 
nitrate-nitrogen 26 pounds per acre; total nitrogen 2900 pounds; phosphorus 
1104 pounds; potassium 25,130 pounds; calcium 4510 pounds; magnesium 4520 
pounds; and iron 47,800 pounds. Besides these the soil contains 840 pounds 
of manganese and 121,000 pounds of aluminum per acre. 

TABLE 3 

Physical analysis of the soil (grades of Bureau of Soils) 



CONSTIXDENTS 


SIZE OF 
PARTICLES 


CRAY SILT 


YELLOW GRAV 
SILT 


YELLOW SILT 




2-1* 
1.0 -0 5 
0.5 -0.25 
0.25-0.1 
0.1 -0.05 
0.05-0. 005 
0.005 


percent 

1.76 
0.93 
2.15 
5.77 
10.93 
25.26 
44.61 
10.15 


percent 

1.36 

1.37 

1.79 

2.57 

4.09 

20.72 

50.99 

18.45 


percent 

1 61 




00 




21 




0.44 




97 




52 35 


Silt 


19 54 




26.47 






Total 




99 80 


99.99 


99.98 



' Calculated on water-free basis. 



Yellow gray silt loam. This was taken from the farm of Joseph Quizlell at 
Carmi, White County, Illinois. It contains 98.64 per cent of dry matter. 
The reaction is acid and the lime requirements amount to 2814 pounds of lime- 
stone per acre. The essential plant-food elements found amount to 36 pounds 
of nitrate nitrogen per acre; 1370 pounds of total nitrogen; 693 pounds of 
phosphorus; 35,800 pounds of potassium; 3920 pounds of calcium; 4180 pounds 
of magnesium; and 74,200 pounds of iron. The manganese and aluminum 
found amount to 786 pounds and 151,000 pounds, respectively. 

Yellow silt loam. This was taken near Vienna, Johnson County. It con- 
tains 98.39 per cent of dry matter. The reaction is acid and the lime require- 
ment amounts to 2921 pounds per acre. The essential plant-food elements 
run up to 60 pounds of nitrate-nitrogen per acre; 1966 pounds of total nitrogen; 
691 pounds of phosphorus; 29,000 pounds of potassium; 7850 pounds of cal- 
cium; 5330 pounds of magnesium and 74,200 pounds of iron. Manganese and 
aluminum reached 660 pounds and 14,900 pounds per acre, respectively. 



TABLE 4 
Gray sill loam 



Determined 

Dry matter 

Acidity 

Aluminum 

Calcium 

Iron 

Magnesium. ... 

Manganese 

Nitrate-nitrogen 

Nitrogen 

Phosphorus. ... 
Potassium 

Determixed 

Dry matter 

.•\cidity 

Aluminum 

Calcium 

Iron 

Magnesium 

Manganese 

Nitrate-nitrogen 

Nitrogen 

Phosphorus 

Potassium 

Detkrmi.\-ed ; . . 

Dry matter 

Acidi'y 

Aluminum 

Calcium 

Iron 

Magnesium 

Manganese 

Nitrate-nitrogen 

Nitrogen 

Phosphorus 

Potassium 



P. p.m. I 



9cS8 

60,500 

2,255 

23,900 

2,260 

420 

13 

1,450 

550 

12,560 



2,125 

121,000 

4,510 

47,800 

4,520 

840 

26 

2,900 

1,104 

25,130 



EXTRACTED WITH KNO) 



P.p.I 



30 

33,400 

2,225 

18,300 

2,250 

400 

29 

1,451 

481 

40,140 



96.96 

44.79 
1.53 

23.85 
0.43 
4.76 

22.693 

4 

12.54 
28.95 



EXTRACTED WrTH H:0 



P.p.m. 



925 

49,800 

2,253 

22,100 

2.259 

415 

11 

1,450 

549 

12,420 



7.31 
17.67 
0.08 
7.53 

1.19 
15.39 

4 

< 

1.11 



Yellow gray silt loam 



P.p.r 



1,358 

75,600 

1,960 

20,100 

2,095 

393 

18 

685 

336 

17,900 



2,813 

151,200 

3,920 

40,300 

4,180 

786 

36 

1,370 

693 

3.^800 



EXTRACTED WITH KNO: 



P.p.t 



11 
30,300 

1,950 

16,700 

2,090 

391 

40 

690 

275 

24,100 



99.93 
59.93 
0.51 
14.44 
i 

3.03 
55.00' 

4 

18.1.5' 
25.72 



EXTR.4CTED WITH H=0 



P.p.m. 



1,260 

58,900 

1,958 

19,600 

2,090 

389 

15 

689 

335 

17,880 



7.21 
24.73 

4 

2.4S 

1.02 
16.66 

4 

0.11 



Yellow silt loan 



EXTRACTED WITH KXOj 



EXTRACTED 1 



P.p.I 



1,318 

74,700 

3,425 

37,100 

2,665 

330 

30 

983 

346 

14,500 



P.p.I 



2,921 

149,400 

7,850 

74,200 

5,330 

660 

60 

1,966 

691 

29,000 



28 

36,900 

3,400 

2,930 

2,660 

301 

315 

983 

292 

22,300 



P.p.m. 



97.93 
50.61 
0.72 
21.01 

4 

8.79 
90.47' 

4 

15.61 

28.57' 



1,155 

58,600 

3,410 

33,900 

2,664 

325 

23 

981 

339 

14,400 



13.36 
21.55 
0.43 
8.62 

4 

1.51 
23.33 

4 

2.02 
0.69 



' CaCOs. 

* Limestone requirements 2,000,000 pounds of soil. 
' Increase. 

* Within the limits of probable error. 

168 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 169 

While a considerable amount of a calcium is present in these soils, qualita- 
tive tests for carbonates showed only traces, which indicate that these soils 
are deficient in calcium carbonate. It may be added further that while these 
soils are well provided with potassium, the phosphorus and nitrogen contents 
are rather low. On the other hand, the aluminum content is very high. 

Sweet clover (biennial variety) was the crop used in this work for the reason 
that it does not thrive in strongly acid soils, and will, therefore, respond more 
readily to soil treatment. Inoculated seeds were used in every case. 

The experiments were carried out in 1-gallon pots, each holding about 5 
kgm. (11 pounds) of soil. 

Experiment I. Effect of aliiminnm salts, alone and in combination with calcium 
carbonate or with acid phosphate on sweet clover grown in sand 

Three salts, aluminum sulfate, aluminum chloride and aluminum nitrate, 
and one hydroxide, aluminum monohydroxide, were used. When applied 
alone the chemicals were used in three different amounts, one, for the sake of 
convenience, is called normal application, the second, one-fifth the normal, and 
the third, five times the normal application. The basis for the normal appli- 
cation is the acidity or lime requirement of the yellow silt loam, which is 2921 
pounds limestone per acre, or 6.79 gm. calcium carbonate per 5 kgm. of soil. 
In other words, the normal application is the chemical equivalent of the salts 
to 6.79 gm. of calcium carbonate. In combination with calcium carbonate or 
with acid phosphate the salts remained constant while calcium carbonate and 
acid phosphate were applied in three different amounts, normal, one-fifth nor- 
mal and five times normal. The normal apphcation of calcium carbonate is 
the lime requirement of the soil and that of acid phosphate the chemical 
equivalent to the normal application of the salts. For the sake of brevity, 
hereafter throughout the discussion, we will refer to these three different 
amounts as the normal, the minimum, and the maximum application. 

The chemicals were thoroughly incorporated in the sand, and seeds of 
sweet clover were sown. In order to insure a sufficient number of good seed- 
lings the seeds were sown rather freely, but as the plants grew they were grad- 
ually thinned out until finally only five plants were left in each pot. The 
plant-food solutions were prepared and applied as directed in Hopkins and 
Pettit's "Soil Fertility Laboratory Manual" (34). Two crops have been 
grown in this series. The first was planted on July 17 and harvested Novem- 
ber 1, 1919; the second was planted on January 19, but because of some un- 
known causes the seedlings failed to attain a uniform stand, so the whole 
series was replanted on February 2. The crop was harvested on May 21. 
The yields for two crops are given in table 5. 

During the first crop several things were observed which led up immediately 
to the setting up of another series, and to the introduction of some modifica- 
tions in the treatment of the pots for the second crop. In the first place, it 
was noticed that on every pot receiving acid phosphate no plant would grow. 



170 



JOSE JISON \URASOL 



Since the application of acid phosphate was rather heavy, 964 pounds to the 
acre or 5.3 gm. per pot, it was thought that tlie failure of the plants to grow 
might have been due to excessive amounts of acid phosphate present rather 
than to the presence of aluminum; accordingly a new series with acid phos- 
phate alone, and in combination with calcium carbonate, was set up. This 
was designated as 600 series. The results of this series are shown in plate 6. 
It proved the supposition true that acid phosphate in such amounts was in- 
jurious to seedlings. Even calcium carbonate in amounts sufficient to neu- 
tralize the acidity of the acid phosphate did not prevent the harmful effect of 
acid phosphate. With this experience the application of acid phosphate was 
reduced to from 100 to 400 pounds to the acre, in the second planting. 

TABLE 5 

Ahiiiihnim scries {dry weight of five plants) 



ll 


o 


|i 


S 3 


o 

H 


^ Zi 


1 


II 


|i 


1 


c i 


J 


1 




sm. 


gm. 




gm. 




sm. 


jra. 




sm. 


gm. 


1 


sm. 


101 


3.40= 


9.73 


201 


4.10 


301 


3.50 


8.89 


401 


9.13 


11.11 


411 


8.51 


lo: 


0.00 


3.60 


202 


0.00 


302 


0.00 


1.85 


402 


8.74 


14.07 


412 


10.42 


103 


2.85 


8.20 


203 


0.00 


303 


1.40 


8.02 


403 


10.80 


12.29 


413 


0.00 


104 


0.00 


0.00 


204 


0.00 


304 


0.00 


0.00 


404 


3.67 


12.14 


414 


7.14 


105 


16.59 


13.06 


205 


17.15 


305 


11.99 


11.68 


405 


15.41 


13.24 


415 


9.16 


106 


1.65 


5.50 


206 


0.80 


306 


4.22 


5.38 


406 


13.13 


11.38 


416 


14.87 


107 


18.52 


10. W 


207 


16.07 


307 


16.17 


19.73 


407 


9.36 


9.74 


417 


14.03 


lOS 


0.00 


2.72 


208 


0.00 


308 


0.00 


2.55 


408 


00 


10.56 


418 


00 


109 


0.85 


2.02 


209 


0.00 


309 


4.00 


1.93 


409 


20 00 


11.68 


419 


9.72 


110 


0.00 


4.07 


210 


0.00 


310 


000 


6.56 


410 


0.00 


14.50 







' Harvested at the age of 106 days. 

- -Average of 2 pots. 

' Harvested at the age of 108 dav.^. 



The second observation made v,-as on the showing of the plants in the con- 
trol pots of every series, e.xcept those of the aluminum monohydro.xide series. 
The plants in these pots appeared to be suffering from lack of some elements. 
Since the plant-food solution applied to the pots did not contain calcium, it 
was thought that the plants in the controls might have been suffering from lack 
of calcium, in which case the results of the different treatments would not be 
comparable. Following this thought it was planned for the second crop to 
apply calcium silicate to each pot as a source of calcium, and in quantities 
having calcium equal to the amount contained in calcium carbonate applied 
as normal. 

The third observation made was on the aluminum monohydroxidc series in 
which all pots except those receiving the maximum amount of aluminum mono- 
hydroxide, and acid phosphate, show no effect of the presence of aluminum. 



ALUmNUM AS A FACTOR IN SOIL ACIDITY 171 

This compound, being insoluble, will produce no toxic effect, but it was thought 
that adding some substances which would yield acids on decomposition might 
change the aluminum hydroxide into a soluble form of aluminum, thus throw- 
ing further light on the form of aluminum compounds in the soil that produce 
toxicity. So it was planned for the next crop to introduce ammonium sulfate 
and dried blood in the series. Then the aluminum chloride series was dropped 
out in order to give way to this plan. Following is the plan of the experi- 
ments. Every treatment was carried out in duplicate. 

Plan of the Experiment 

100 Series — Aluminum sulfate, .^U (SOi)! 

7.75 gm., or 3100 lbs. to the acre Al2(S04)3 = 6.79 gm. CaCOj 

.S.3 gm., or 964 lbs. to the acre CaHi(P04)2 = 7.75 gm. Al2(S04)j according to the 
following equation: 

2Al2(S04)3 + CaH4(P04)2 = 2A1P04 + CaS04 + 2H2SO4 

101. Control— Plant-food only 

102. Plant-food + 7.75 gm. Al2(S04)3 

103. Plant-food + J, or 1.55 gm. Al2(S04)3 

104. Plant-food -t- 5 X 7.75 gm., or 38.75 gm. Al2(S04)3 

105. Plant-food + 7.75 gm. Al2(S04)3 -|- 6.79 gm. CaCOj 

106. Plant-food + 7.75 gm. Al2(S04)3 -t- 5, or 0.36 gm. CaCOj 

107. Plant-food -|- 7.75 gm. Al2(S04)3 -f 5 X, or 33.95 gm. CaC03 

108. Plant-food -f 7.75 gm. AUOO,), -f 5.3 gm. CaH4(P04)2 

109. Plant-food + 7.75 gm. Al2(S04)3 + i, or 1.06 gm. CaHi(P04)2 

110. Plant-food + 7.75 gm. Al2(S04)3 -F 5 X, or 26.5 gm. CaH4(P04)2 

200 Series — Aluminum chloride, AICI3 

6.04, or 2405 pounds to the acre AICI3 = 6.79 gm. CaCOa 

5.3 gm., or 964 pounds to the acre CaH4(P04)2 = 6.04 gm. AICI3 according to the fol- 
lowing equation: 

2.\lCl3 -I- CaH4(P04)2 = 2.\1P04 -|- CaCU -|- 4HC1 

201. Control— Plant-food only 

202. Plant-food + 6.04 gm. AICI3 

203. Plant-food -hi, or 1.21 gm.AlCU 

204. Plant-food -f 5 X, or 30.2 gm. AICI3 

205. Plant-food + 6.04 gm. AICI3 -1- 6.79 gm. CaC03 

206. Plant-food + 6.04 gm. AICI3 -1- i, or 1.36 gm. CaCOj 

207. Plant-food -|- 6.04 gm. AICI3 -|- 5 X, or 33.95 gm. CaCOj 
20s. Plant-food -|- 6.04 gm. AICI3 -|- 5.3 gm. CaHjCPO,). CaCOj 

209. Plant-food -|- 6.04 gm. AICI3 + i, or 1.06 CaH4(P04)2CaCO, 

210. Plant-food + 6.04 gm. .-VlClj -|- 5 X, or 26.5 CaH4(P04)2CaC03 

300 Series — Aluminum nitrate, A1(N03)3 

9.65 gm., or 3859 pounds to the acre A1(N03)3-9H20 X 6.79 gm. CaCOs 
5.3 gm., or 964 pounds to the acre CaH4(P04)2 = 9.65 gm. Al(N03)j according to the 
following equation: 

2 A1(N03)3 -I- CaH4(P04)2 = 2AIPO4 -|- CaNOs -|- 4HN0, 

301. Control— Plant-food only 

302. Plant-food -|- 9.65 gm. A1(N03)3 

303. Plant-food -|- J, or 1.93 gm. AKNO,), 



172 JOSE JISON MIRASOL 

304. Plant-food + 5 X, or 46.25 gm-.-UCNO,) J 

305. Plant-food + 9.65 gm. .\1(N0>), -f 6.79 gm. CaCO, 

306. Plant-food + 9.65 gm. Al(\Oj)s + i, or 1.36 gm. CaCOj 

307. Plant-food -f 9.65 gm. .'Vl(NO,), -f 5 X, or 33.95 gm. CaCOj 

308. Plant-food + 9.65 gm. .-VKNO,), + 5.3 gm. CaH,(PO<)j 

309. Plant-food -f 9.65 gm. .MCNOj), + h or ].06 gm. CaH4(P04)2 

310. Plant-food + 9.65 gm. .-VKNO,), + 5 X, or 26.5 gm. CaHi(P04), 

■MO Series — Aluminum Hydroxide, A1(0H)3 

3.5 gm., or 1399 pounds to the acre Al(OH)s = 6.79 gm. CaCOj 

7.8 gm. CaH,(PO,)j, or 1418.5 pounds per acre, or 3.5 gm. .^KOH)} according to the 
following equation : 

4 Al(OH)3 + 3 CaIl,(P0,)2 = 4 AlPO, + Ca.,(P04), + 12 H,0 

401. Control-Plant-food only 

402. Plant-food + 3.5 gm. A1(0H)3 

403. Plant-food -f J, or 0.7 gm. A1(0H)3 

404. Plant-food -|- 5 X, or 17.5 gm. A1(0H)3 

405. Plant-food + 3.5 gm. AUOH), + 6.79 gm. CaCO, 

406. Plant-food -|- 3.5 gm. Al(OH)3 -f- i or 1.36 gm. CaCOs 

407. Plant-food + 3.5 gm. Al(OH)3 -f 5 X , or 33.95 gm. CaC03 

408. Plant-food -|- 3.5 gm. A1(0H)3 + 7.8 gm. CaH^lPO,)^ 

409. Plant-food -f 3.5 gm. A1(0H)3 + i, or 1.5 gm. CaHjlPOi^j 

410. Plant-food -f 3.5 gm. .\l(OH)3 + 5 X, or 39.0 gm. CaHiCPOi 

600 Series— Acid phosphate, CaH,(P04)8 

601. Control — Plant-food only 

602. Plant-food + 5.3 gm. CaHiCPOs 

603. Plant-food -|- ], or 1.06 gm. CaH4(P04)2 

604. Plant-food -f- 5 X, or 26.5 gm. CaH,(P04)i 

605. Plant-food 4- 5.3 gm. CaH4(P04), + 6.79 gm. CaCOs 

606. Plant-food -f 5.3 gm. CaH.CPOJs -f i, or 1.36 gm. CaCO, 

607. Plant-food -|- 5.3 gm. CaHiCPOi)^ -f 5 X, or 33.95 gm. CaC03 

PLAN FOR SECOND CROP 

100 Series. The same as before with the addition of 7.9 gm. CaSi03 to each pot and 
the reduction of the acid phosphate application to from 100 to 400 pounds to the acre, or 
from 350 mgm. to 1.00 gm. per pot. 

3J0 Series. The same plan as before with the same modification noted in the 100 series. 
400 Series. Up to 410, inclusive, the same plan as before with the same modification as 
noted in the 100 series. 

From 411 to 424 the following arrangement has been followed: 

From 411 to 417, inclusive, 4.4 gm. (NHijjSOi has been added according to the following 
reaction : 

(NH4)2S04 —■ 2HN0, plus HjSO, 
but 3 HNOs -. Al(OH), 
and 3H,S04 -> 2 Al(OH), 
or 132 gm. (NH4)2S04 = 104 A1(0H)3 
.-. 3.5 gm. Al(OH), = 4.4 gm. (NH4)jS04 
From 418 to 424, inclusive, 13.33 gm. of dried blood has been added, according to the 
oUowing reaction. The dried blood used contained 14 per cent N. or 17 gm. NH». 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 173 

If all ammonia produced is nitrified, 2 HNO3 is produced. 
But HNO3 = Al(OH)3 
.-. 189 gm. HNO3 = 78 gm. A1(0H)3 
3.5 gm. A](0H)3 = 8.4 gm. HNO3, or 13.33 gm. dried blood 

411. Plant-food + 3.5 gm. AKOH), + 4.4 gm. (NH4)2S04 + 7.9 gm. CaSiO, 

412. Plant-food + 3.5 gm. A1(0H)3 -|- i or 0.88 gm. (NHijjSOi -|- 7.9 gm. CaSiO, 

413. Plant-food -f 3.5 gm. A1(0H)3 -f 5 X , or 0.22 gm. (NHijsSO, + 7.9 gm. CaSiO, 

414. Plant-food -|- 17.5 gm. Al(OH)3 -|- 4.4 gm. (NH^jjSO, + 7.9 gm. CaSiOj 

415. Plant-food -f 3.5 gm. A1(0H)3 + 4.4 gm. (NH4)2S04 + 7.9 gm. CaSiOa 

416. Plant-food -|- 3.5 gm. A1(0H)3 -|- 4.4 gm. (NH4)2SOi -f 7.9 gm. CaSiO, 

417. Plant-food + 3.5 gm. Al(OH)3 -|- 4.4 gm. (NH4)2SO^ -f 7.9 gm. CaSiOj 

418. Plant-food + 3.5 gm. A1(0H)3 -t- 13.33 gm. dried blood 

419. Plant-food -+- 3.5 gm. A1(0H)3 4- 5, or 2.66 gm. dried blood 

420. Plant-food -|- 3.5 gm. Al(OH)3 -f 5 X, or 66.65 gm. dried blood 

421. Plant-food -f 17.5gm.AI(OH)3-|- 13.33 gm. dried blood 

422. Plant-food + 3.5 gm. A1(0H)3 + 13.33 gm. dried blood 

423. Plant-food + 3.5 gm. A1(0H)3 + 13.33 gm. dried blood 

424. Plant-food -|- 3.5 gm. Al(OH)3 -|- 13.33 gm. dried blood 

Results and discussion. The effect of aluminum salts, of aluminum hydrox- 
ide and of acid phosphate on the growth of sweet clover, is best shown in the 
photographs in plates 2, 3, 4, 5 and 6. 

In the first crop in which no compound as a source of calcium was appUed 
to the pots, aluminum sulfate proved to be injurious to sweet clover even in 
very small amounts. This may be seen in pots 102, 103 and 104 in which 
aluminum sulfate alone was applied. In pot 104, which received the maxi- 
mum application of the salt, absolutely no seed could germinate. Pot 106, 
receiving the normal application of aluminum sulfate and one-iifth the nor- 
mal application of calcium carbonate, shows that in small amounts calcium 
carbonate cannot correct the toxic effect of aluminum. On the other hand, 
where calcium carbonate has been applied in larger amounts, normal and 
maximum, sweet clover exhibited enormous growth. In the case of pots re- 
ceiving aluminum sulfate and acid phosphate, those receiving 964 pounds and 
4820 pounds of acid phosphate per acre failed to grow any crop. 

What has been said about the effect of aluminum sulfate on sweet clover 
can also be said for aluminum chloride and aluminum nitrate. But with 
aluminum hydroxide the result is different. The normal apphcation of alumi- 
num hydroxide did not have any effect on sweet clover; the maximum, how- 
ever, caused some depression. It is also important to note that whereas in the 
combination of aluminum salts and the minimum acid phosphate application, 
no sweet clover grew, but in that of the almninum hydroxide and minimum 
acid phosphate no effect was shown. This proves that the failure of sweet 
clover to grow in pots 109, 209 and 309 was due to the presence of aluminum 
rather than that of acid phosphate. 

The results of the second cropping, in which calcium silicate was added as 
a source of calcium, and the application of acid phosphate has been reduced 
to from 100 to 400 pounds per acre, were different from those of the first crop. 



174 JOSE JISON MIRASOL 

First, the normal application of aluminum sulfate did not show any toxic 
effect at all, while the maximum application was always fatal to sweet clover. 
Second, in every case where calcium carbonate was applied, no matter in what 
amount, good plants were growing, indicating that active aluminum has been 
put out of action. Acid phosphate in decreased amounts seemed to help in 
reducing the injurious effect of aluminum sulfate. 

The results with aluminum nitrate were different from those noted in the 
case of sulfate. The normal application showed very toxic effects. While 
the maximum application of calcium carbonate was beneficial to clover the 
normal application did not entirely eliminate the to.xicity of aluminum ni- 
trate. The action of acid phosphate in eliminating the toxicity of aluminum 
nitrate was much less pronounced than in the case of the sulfate. From this 
difference of the behaviour of sweet clover on the two salts we are led to conclude 
that aluminum nitrate chemically equivalent to the acidity of the soil is more 
toxic than aluminum sulfate. 

In the case of aluminum hydroxide, up to pot 419 with the exception of pots 
413 and 419, the stand of sweet clover was uniform. Even the maximum ap- 
plication did not produce any effect on the growth of the plants. Pot 413 
received 22 gm., the maximum application, of ammonium sulfate. The fact 
that sweet clover did not grow cannot be attributed to any cause but to an 
excessive amount of ammonium salt which, on breaking down, liberates 
ammonia that causes injury to the germinating seeds. Pot 418 received 13.33 
gm., the normal application, of dried blood. Pot 419 received 2.66 gm., the 
minimum application, of dried blood. And the fact that on the former noth- 
ing grew, while on the latter the crop was as good as that in any other pot in 
the series, can be attributed also to the excessive amount of dried blood which 
on decomposition produces ammonia that hinders the germination of seeds. 
Apparently neither ammonium sulfate nor dried blood in smaller amounts was 
able to change aluminum hydroxide into other forms of aluminum which could 
produce the same effect as aluminum sulfate or nitrate. 

The effect of aluminum salts on sweet clover in the presence of calcium carbon- 
ale. In the series with aluminum sulfate, chloride and nitrate we have noted 
that in the presence of an excess of calcium carbonate the toxicity of the salts 
was o/ercome. Ruprecht and Morse (60) found this to be true also in their 
water-culture investigation with aluminum and iron sulfates in which, when- 
ever calcium carbonate was added in excess to the solution containing alumi- 
num and iron, the to.xicity of these metals has been eliminated and good 
healthy plants grew in the solution. With this fact the question naturally 
arises as to what became of the aluminum. The most logical conclusion would 
be that aluminum had entered into combination with other elements forming 
an insoluble compound. Ruprecht and Morse (60) suggested that aluminum 
was precipitated as hydroxide and as such had no effect on the plants grown in 
the solution. The results of the test carried out in this work proved that 
aluminum monohydroxide has no effect on sweet clover. But whether the 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 175 

hydroxide precipitated by the introduction of calcium carbonate is the variety 
that does no't dissolve in water, acid and alkali, the author seriously doubts. 
In fact, he is of the opinion that the aluminum hydroxide precipitated by the 
introduction of calcium carbonate is like that formed when ammonia and so- 
dium or potassiuum hydroxide is added to a solution containing aluminum. 
This is aluminum trihydroxide, which is insoluble in water and would there- 
fore have no effect on the plants grown in solution. But this form of hydrox- 
ide is soluble even in dilute acids (53), and in sand or soil where chemical 
changes are constantly taking place this form of aluminum hydroxide will 
not remain long, for it will be converted into aluminum sulfate, chloride and 
nitrate as fast as free sulfuric, hydrochloric and nitric acids are produced in the 
soil and as long as the soil is not supplied with calcium or other suitable bases. 
For this reason the author looks into the formation of a more stable aluminum 
compound as an explanation for the elimination of active aluminum when cal- 
cium carbonate is added to sand or soil. He is of the opinion that as soon as 
calcium bicarbonate is formed by the action of carbonated water on calcium 
carbonate, the bicarbonate reacts with the aluminum salts forming calcium 
aluminate. The reaction may be written as follows: 

Al2(S04)3 + 3Ca(HC03)2 = Al203.3CaO + CaSOi + 3H2O.6CO2 

Calcium aluminate is one of the constituents of portland cement and is a 
very stable compound. The formation of this compound seems to be the only 
satisfactory explanation for the ineffectiveness of aluminum as a toxic sub- 
stance in the presence of sufficient calcium carbonate. 

The effect of alumintim salts on sweet clover in the presence of acid phosphate. 
Mention has been made before that the 964 pounds per acre application of 
acid phosphate proved to be detrimental to sweet clover, and that the failure 
of the crop in the pots which received the normal and maximum application 
was brought about by the excess of acid phosphate. But in the second crop 
where the acid phosphate was applied in reduced amounts from 100 to 400 
pounds per acre, the results showed that acid phosphate reduced the to.xicity 
of aluminum. While the pots receiving the rhinimum and normal apphcation 
in series 300 did not show any reduction of the toxicity of aluminum nitrate, 
the reduction of toxicity in the pot receiving 400 pounds of acid phosphate 
per acre is very pronounced, as indicated by the fairly good growth of the 
plants. Evidently the minimum and normal applications were not sufficient 
to convert the larger portion of aluminum into an insoluble form. Now the 
question arises as to how acid phosphate reduced the toxicity of aluminum. 
The answer is that vnih acid phosphate, aluminum sulfate, chloride and ni- 
trate form an insoluble compound. In this case the compound is aluminum 
phosphate and is formed according to the following reaction: 

2A1(N03)3 + CaH4(P04)2 = 2AIPO4 + Ca(N03)2.4HN03 



176 JOSE JISON JQRASOL 

Under soil conditions this reaction is probably never complete; nevertheless, 
a great amount of insoluble aluminum phosphate is formed. But the free ni- 
tric acid formed might also react with more aluminum, thus repeating the pro- 
cess until equiUbrium is finally reached. Aluminum phosphate is highly in- 
soluble and Wheeler (82) thinks that in the case of acid soils it is desirable to 
apply lime before or at the same time with acid phosphate in order to prevent 
formation of aluminum ])hosphate which is even more insoluble than trical- 
cium phosphate. 

Experiment If. Effect of limestone and acid phosphate alone and in combination 
on the productivity and acidity of acid soils 

Ten duplicate pots for each type of soil were filled with about 5 kgm. (11 
pounds) of soil, and treated according to the following plan: 

PLAN OF THE EXPERIMENT 

700 Series — Gray silt loam 

.\cidity = 4.94 gm. CaCOj per 5 kgm., or .S.3 gm. limestone of 93 per cent purity, or 
2125 pounds to the acre. 

701. Control (nothing) 

702. Soil + 5.3 gm. limestone 

703. Soil + 5, or 1.0 gm. limestone 

704. Soil -I- 5 X, or 26.5 gm. limestone 

705. Soil -t- 5.8 gm. CaH,(P04)s = 1.05 tons to the acre 

706. Soil + i, or 1.16 gm. CaH,(P04)2 = 0.21 tons to the acre 

707. Soil -I- 5 X, or 29 gm. CaKiiPOilj = 5.25 tons to the acre 

708. Soil + 5.8 gm. CaIl,(P04)2 = 5.3 gm. limestone 

709. Soil -I- 5.8 gm. CalliCPOOs = i, or 1.06 gm. limestone 

710. Soil + 5.8 gm. CaHjCPOs = 5 X, or 26.5 gm. limestone 

SOO Series — Yeitow gray sill loam 

Acidity = 6.5 gm. CaCOj per 5 kgm., or 2813 pounds limestone to the acre 

801. Control 

802. Soil + 7.03 gm. limestone 

803. Soil -|- 5, or 1.40 gm. limestone 

804. Soil -|- 5 X, or 35.15 gm. limestone 

805. Soil -I- 7.6 gm. CaH4(P04)2 = 1.4 tons to Uie acre 

806. Soil + i, or 1.5 gm. CaHiCPOi)^ = 0.28 tons to the acre 

807. Soil -H 5 X, or 38.0 gm. CaH,(P04)2 = 6.00 tons to the acre 

808. Soil + 7.6 gm. CaH4(P04)2 + 7-03 gm. limestone 

809. Soil -1- 7.6 gm. CaH4(P04)2 -i- L or 1.40 gm. limestone 

810. Soil + 7.6 gm. CaH4(P04)2 + 5 X, or 35.15 gm. limestone 

900 Series — Yellow sill loam 

.\cidity -|- 6.79 gm. CaCOj per kgm., or 7.4 gm. limestone, or 2921 pounds limestone to 
the acre. 

901. Control. 

902. Soil + 7.3 gm. limestone 

903. Soil -|- I. or 1.46 gra. limestone 



ALUIlDNUM AS A FACTOR IN SOIL ACIDITY 



177 



904. Soil + 5 X, or 36.5 gm. limestone 

905. Soil + 7.6 gm. CaH4(P04)2, or 1.4 tons to the acre 

906. Soil + i, or 1.58 gm. CaHiCPO,)!, or 0.28 tons to the acre 

907. Soil + 5 X, or 39 gm. CaH4(POi)2, or 6.00 tons to the acre 

908. Soil + 7.8 gm. CaH4(P04)2 + 7.3 gm. limestone 

909. Soil + 7.8 gm. CaH4(P04)2 + J, or 1.46 gm. limestone 

910. Soil + 7.8 gm. CaH4(P04)2 + 5 X, or 36.5 gm. limestone 

Two crops have been harvested in these series. The first was planted on 
August 22, 1919, and harvested November 30, 1919, a period of only 100 days. 
The time of cropping could have been prolonged, but when the crop was moved 
into the greenhouse, the red spider infested it so badly that it was thought best 
to cut the crop down in order to eradicate the red spider at once. The second 
crop was planted on January 16, 1920, and harvested May 21, 1920, after a 
period of 125 days. The yield of the crops is given in table 6. 

TABLE 6 
Scfil series (dry weight of Jive plants) 



GRAY Sn.T 


\i;llow gray silt 


YELLOW SILT 


Series 
number 


First crop' 


Second crop^ 


Series 
number 


First crop 


Second crop 


Series 
number 


First crop 


Second 
crop 


701 
702 
703 
704 
705 
706 
707 
70S 
709 
710 


sm. 

0.54= 

0.81 

0.70 
1.28 
0.87 
0.58 
1.12 
1.65 
0.76 
1.43 


gm. 

2.02 

2.77 
2.07 
5.35 
2.20 
1.62 
3.18 
5.88 
1.58 
7.42 


801 
802 
803 
804 
805 
806 
807 
808 
809 
810 


gm. 
0.27 

0.68 
0.26 
0.97 
0.40 
0.23 
0.67 
0.71 
0.34 
1.45 


gm. 

0.40 
2.29 
0.26 
3.45 
0.60 
1.68 
1.48 

10.58 
1.80 

14.67 


901 
902 
903 
904 
905 
906 
907 
908 
909 
910 


sm. 

0.52 
0.64 
0.52 
1.41 
0.75 
0.62 
1.21 
1.19 
0.71 
1.66 


gm. 

0,79 
1.26 
1.29 
2.11 
4.72 
1.38 
1.45 
4.67 
1.10 
6.49 



• Harv'ested at the age of 106 days. 

- .\verage of 2 pots. 

' Harvested at the age of 108 days. 

For each type of soil a corresponding set of treated pots was laid aside, 
without plants for acidity determination. Two determinations were made, 
the first on December 8, 1919, after a lapse of 108 days from the time the pots 
were set aside, and the second on February 16, 1920, a period of 70 days after 
the first determination. Table 7 shows the results of these determinations. 

ResuUs and discussion. The effect of lime and acid phosphate on sweet 
clover grown on acid soils can best be seen in the photographs in plates 6, 7, 
and 8. It can be seen that all the three types of soil respond to liming. The 
normal and maximum applications especially brought excellent results. The 
plants were healthy, vigorous and dark green. Limestone applied in amounts 
equal to one-fifth of the lime requirement did not benefit the soil at all. The 
growth of the plants in this case was comparable to that of the control in which 



JOSE JISON M3RAS0L 



TABLE 7 
Acidity determinations oj treated soils 



SAMPLED DECEVBER 8, 1919 



1 Acidity I Acidity Acidity 
reduced [ above or reduced 
after 108 below ] due to 
days control treatment 



SAMPLED lEBRfAKY 16, 1920 



Acidity 

reduced 

a/lerl78 

days 



Acidity 
above or 
below 
coDtrol 



Acidity 
reduced 
between 
dates of 
sampling 



Acidity 
reduced 
due to 

treatment 



Gray silt loam. Original acidity — 988 parts per million, or 2125 pounds of limestone per 

acre 







per cent 


per cent 


per cent 




per cent 


per cent 


per cent 


per cent 


701 


705 


28.66 






685 


30.87 




2.83 




702 


165 


83.29 


76.59 


54.63 


74 


92.51 


89.19 


55.15 


62.64 


703 


MO 


35.22 


9.22 


6.56 


425 


56.98 


37.95 


33.59 


26.11 


704 


26 


97.26 


96.31 


68.60 


Alkaline 


100.00 


0.00 


0.00 




705 


545 


44.83 


22.69 


16.17 


217 


78.03 


68.32 


41.83 


47.16 


706 


810 


18.01 


12.96 




687 


30.46 


0.29 


15.18 




707 


467 


52.85 


33.75 


24.19 


115 


88.35 


83.19 


75.37 


57.48 


708 


106 


89.27 


84.96 


60.61 


Alkaline 


100.00 


0.00 


0.00 




709 


437 


56.78 


38.96 


21.12 


243 


75.40 


64.52 


44.39 


44.53 


710 


20 


97.97 


96.32 


69.31 


Alkaline 


100.00 


0.00 


0.00 





Yellow gray silt loam. Original acidity — 1358 parts per million, or 2813 pwunds of limestone 

per acre 



801 


1066 


21.63 






970 


28.57 




9 00 




802 


42 


96.90 


96.06 


75.27 


Alkaline 


100.00 


0.00 


0.00 




803 


542 


60.09 


49.06 


38.46 


362 


73.34 


61.64 


33.21 


44.7 


804 


Alkaline 


100.00 


0.00 




Alkaline 


0.00 


0.00 


0.00 




805 


764 


43.00 


28.33 


21.37 


580 


57.29 


40.20 


24.08 


28.62 


806 


895 


33.28 


16.04 


11.65 


894 


34.16 


7.83 


0.11 


5.59 


807 


479 


63.91 


55.09 


42.28 


271 


80.04 


72.06 


41.33 


51.47 


808 


110 


91.91 


90.62 


70.28 


.\taline 


100.00 


0.00 


0.00 




809 


565 


65.75 


46.43 


44.12 


519 


61.78 


46.49 


8.01 


33.21 


810 


Alkaline 


100 00 


00 


0.00 


Alkaline 


100 00 


0.00 


0.00 





Yellow silt loam. Original acidity — 1318 parts per million, or 2921 pounds of limestone 

per acre 



90: 
902 
903 
904 
905 
906 
907 
908 
909 
910 



685 


48.02 






77 


94.16 


88.76 


46.13 


511 


61.22 


25.40 


13.20 


Alkaline 


0.00 


0.00 




630 


52.20 


8.26 


4.18 


832 


36.71 


17.66 




455 


65.47 


33.57 


17.45 


109 


91.72 


84.09 


43.70 


846 


35.81 


19.05 




16 


98.78 


96.21 


50.76 



683 


48.18 




0.29 


13 


99.01 


98.09 


83.11 


243 


81.56 


64.42 


52.44 


Alkaline 


0.00 


0.00 


0.00 


441 


65.78 


35.43 


30.00 


645 


51.06 


5.56 


22.47 


123 


90.66 


81.99 


72.96 


Alkaline 


100.00 


0.00 


0.00 


642 


51.29 


6.00 


24.11 


Alkaline 


100.00 


0.00 


0.00 



50.83 
33. 3S 

17.60 

2.88 
52 4-8 
0.00 
3.11 



ALUMINTM AS A FACTOR IN SOIL ACIDITY 179 

the plants were very small and chlorotic. The results with acid phosphate 
applied alone, showed that the soils also respond to phosphate fertilization. 
Judging from the growth of the plants even the minimum application seems 
to have benefited the soil. In the first crop, however, the plants looked differ- 
ent from those growng on limed pots. The plants grew more than those in 
the control, but they were slender, branchless, and chlorotic as compared 
with the bushy dark green plants growng on the limed pots. In the second 
crop, excepting the crops in the pots which received the minimum applica- 
tion, those defects observed above have disappeared, and although growth was 
slow during the winter da3's, the plants were healthy, bushy and deep green. 
The best crop in this series was noted in the pots recei\dng the normal apphca- 
tion and maximum application of limestone, together with the normal applica- 
tion of acid phosphate. Even the minimum application of limestone in com- 
bination wth the normal amount of acid phosphate grew better crops than the 
normal appUcation of limestone alone. In the first crop, however, the plants 
were also chlorotic, although to a lesser e.xtent than those in pots receiving acid 
phosphate alone. In the second crop chlorosis has completely disappeared. 

.\f ter the first acidity determination it was found that the acidity of the im- 
treated soil has been reduced also. The acidity of the gray silt loam has been 
reduced 28 per cent, that of the yellow gray silt 21i per cent and that of the 
yellow silt 48 per cent. Up to this time, for a period of 108 days, tap-water 
was used for watering the plants and the pots, but since then rain-water was 
used instead. Experience in the use of this tap-water in the greenhouse proved 
that it has a tendency to reduce the acidity of acid soUs. For example, a very 
acid soil watered by the tap-water became alkaline after a few years. Thefact 
that the acidity of the controls of the three t}-pes of soil have been reduced is 
attributed to the use of the tap-water. But by subtracting the per cent of 
acidity reduced in the control from the total acidity of the treated pots, we 
still have a fair indication of the acidity reduced due to the treatment of the 
soils. 

The efltect of limestone and acid phosphate alone and in combination on 
the acidity of the three acid soils is best shown in plates 11 and 12, in 
which the treatment of the pots is represented by the abscissas and the per 
cent of acidity reduced by the ordinates. Curve 1 in each figure represents 
the per cent of acidity reduced after 108 days and curve 2 the total acidity 
reduced for a period of 1 78 days. 

The three types of soil responded differently to the different treatments. Of 
the three the yellow gray silt loam responded more readily to liming and phos- 
phate fertilization than either of the other two types. From the charts we 
can see that in 108 days the normal application of limestone or the amount 
required to neutralize the acidity of the soil reduced the acidity of the gray 
silt about 55 per cent, of the \'ellow silt 46 per cent and that of the yellow gray 
silt 76 per cent. In 178 days the total acidity reduced was 63 per cent for 
the gray silt and 51 per cent for the yellow silt; the yellow gray silt was com- 



180 JOSE JISON iaRASOL 

pletely neutralized, the reaction being alkaline. With one-fifth of the normal 
application the acidity was reduced 6.56 per cent in the case of gray silt, in 
108 days; 38 per cent in case of the yellow gray, and 13 per cent in case of the 
yellow silt. At the end of 178 days the lime applied was completely used up 
in the neutralization of one-fifth of the acidity of the soil. In the case of the 
yellow gray silt the percentage of acidity reduced in both determinations ex- 
ceeds that which would theoretically be accomphshed by lime applied in an 
amount equal to one-fifth of the lime requirement. This fact is probably due 
to experimental error which would include samplingandmanipulalion. When 
limestone equal to five times the lime requirement was added, the neutraliza- 
tion of acidity was complete in 108 days in the case of two soils; only 68.8 
per cent of the acidity was reduced in the case of gray sill. All these facts in- 
dicate the rapidity with which calcium carbonate puts active aluminum out 
of action, the substance responsible for the acidity of the soils. 

The effect of acid phosphate on the three soils is interesting. The notion 
that acid phosphate has the tendency to increase the acidity of a soil has no 
confirmation in this work. On the contrary, the results show that acid phos- 
phate decidedly reduced the acidity of the soil, as measured by the Hopkins 
method. The reaction, however, is slower than that in the case of calcium 
carbonate. In 108 days the normal application of acid phosphate destroyed 
16 per cent of the acidity of the gray silt; 21 per cent of that of the yellow gray 
silt; and 4 per cent of that of the yellow silt. At the end of 178 days 47 per 
cent of the acidity of the gray silt was destroyed; 28 per cent of that of the 
yellow gray silt and only 17 per cent of that of the yellow silt. Applied in one- 
iifth the normal appUcation, acid phosphate reduced in 178 days the acidity of 
the gray silt 7 per cent; of the yellow gray silt 12 per cent; and of the yellow 
silt only 3 per cent. In five times the normal application acid phosphate re- 
duced the acidity of the gray silt 24 per cent in 108 days and 57 per cent in 
178 days; of the yellow gray silt 42 per cent in 108 days and 51 per cent in 178 
days; of the yellow silt 17 per cent in 108 days and 52 per cent in 178 days. 

The combination of acid phosphate and limestone produced a still more 
interesting result. The combination of the normal application of limestone 
and acid phosphate reduced, in 108 days the acidity of the gray silt 60 per 
cent; of the yellow gray silt 70 per cent; and of the yellow silt 43 per cent. 
Afte- 178 days all the pots with this treatment were alkaline. The combina- 
tion of the normal application of acid phosphate and one-fifth the normal dose 
of limestone also reduced considerably the acidity of the soils. But wth the 
combination of the normal application of acid phosphate and the maximum of 
limestone, the yellow gray silt was alkaline in 108 days, while the gray and 
yellow silt were then reduced 69.31 per cent and 50.76 per cent, respectivelv. 
At the end of 178 days the soils were alkaline. 

How acid phosphate reduces the acidity of acid soils. One of the problems in 
the present investigation is whether acid phosphate increases theaciditv of an 
acid soil. Using the calcium-acetate method Hartwell and Pember (27) found 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 181 

that the acidity of acid soils increases as the amount of acid phosphate applied 
was increased. Comparing the lime-water and the potassium-nitrate methods 
Albrecht' found also that with the lime-water method the acidity increased as 
the amount of acid phosphate was increased, but with the potassium-nitrate 
method up to a certain point, the increase of acid phosphate was accompanied 
by a decrease of acidity. The results discussed in the preceding paragraph cor- 
roborate the findings of Albrecht with the potassium-nitrate method. In 
this connection two questions come up. First, if acid phosphate reduced the 
acidity of the soil, how? And second, why are the results between the potas- 
sium-nitrate method on the one hand, and those of calcium-acetate and lime- 
water on the other, so diametrically opposed? 

Hartwell and Pember (27) noted that while the acidity of the soils was in- 
creased with the increase of acid phosphate application the amount of active 
aluminum was decreased. No explanation was offered for this fact, but we 
can safely attribute it to the combination of active aluminum with other ele- 
ments forming an insoluble compound. One of the products of the reaction 
between acid phosphate and active aluminum in the soil is aluminum phos- 
phate, a very insoluble compound. The decrease in the amount of active 
aluminum after acid phosphate has been applied to the soil is, therefore, due to 
the formation of aluminum phosphate. The larger the amount of acid phos- 
phate applied to the soil containing active aluminum, the larger will be the 
amount of aluminum phosphate formed. And since aluminum is largely 
responsible for the acid reaction of the potassium nitrate extract, the larger the 
amount of aluminum converted into phosphate, the smaller will be the amount 
of aluminum that will be brought into solution when an acid soil is extracted 
with potassium nitrate after acid phosphate has been applied. This explains 
the fact that with the potassium-nitrate method the acidity of acid soils de- 
creases as the amount of acid phosphate applied increases. 

We can see from the above explanation that the opposing results obtained 
by the use of the three methods of determining the acidity of the soil are due 
to the difference of the substances determined. The lime-water and calcium- 
acetate methods determine true acidity, and the potassium-nitrate method, 
while originally intended to determine true acidity, actually determines ac- 
tive aluminum. Since acid phosphate has some free phosphoric acid the first 
two methods will record increased acidity as the amount of acid phosphate is 
increased. 

Hartwell and Pember (27) also observed that in spite of the large amount 
of acidity (as determined by calcium acetate) due to acid phosphate, barley 
made a marked growth. In the present investigation the growth of sweet 
clover on pots receiving acid phosphate alone increased as the acid phosphate 
applied increased. But the correlation is between growth and decrease of 
acidity rather than growth and increase of acid phosphate. This is better 

' W. .Mbert .'Mbrecht's unpublished work in the University of Illinois. 



182 



JOSE JISON" MIR.XSOL 



illustrated in table 8 in which the per cent of acidity reduced and the dr_\- 
matter of five plants from each pot are put together. 

The results given are one of the evidences that aluminum is an important 
factor in the acidity of the three types of soil studied. 



Effect of the rediiclion of acidity by acid phosphate on the yield of suee! clover 
Gray silt 





701 
0.54 


705 
16.16 
S7 


706 
5.70 
0.5S 


707 


Per cent of acidity reduced 


24.19 

1.12 









Yellow gray silt 




801 
0.27 


805 
21.37 
0.40 


806 
11.65 
0.23 


807 


Per cent of acidity reduced 


42.28 
0.67 






Yellow slit 


Pot number 

Per cent of acidity reduced 

Dr\' weight (gm.) 


901 905 

4. IS 
0.52 ' 0.75 


906 
1.36 
0.62 


907 
17.45 
1.21 











Exberiment III. 



What happens ivheri acid soils are leached out with potassium 
nitrate or water 



Two pots of each of the three types of soil were leached out with normal 
potassium nitrate until the last 125 cc. of leachings were practically neutral. 
With the gray silt loam 30 liters of the solution per pot were needed to reach 
this point. For the yellow gray silt loam 35 liters were needed, and for the 
yellow silt 39 liters. After leaching with potassium nitrate the soil was leached 
out with distilled water again in order to get rid of the excess of potassium 
nitrate. The leaching was continued also until the last few drops showed 
faintly blue to the diphenylamine sulfuric acid test for nitrates. Then the 
soils were dried out and sampled for analysis. The results of the analysis are 
given in column 3, table 4. 

k similar set was leached out with water alone. Distilled water was used 
in leaching the soils and the operation was continued until the last 125 cc. 
needed hardly 0.5 cc. of the standard sodium hydroxide solution used in ti- 
trating the acidity. When this end was reached, 12 liters of water had been 
used in the gray silt; 16 liters in theyellowgray silt; and 13 liters in the yellow 
silt. Then the soil was dried and sampled as in the above set for analysis. 
The results of the analysis are given in column 5, table 4. 

What has been found from the above experiments may be summarized as 
follows. With potassium nitrate 96.96 per cent of the acidity of the gray silt 



ALUraNUil AS A FACTOR IN SOIL ACIDITY 183 

was extracted, with water only 7.31 per cent of the acidity was extracted. Of 
the aluminum 44.79 per cent was leached out by potassium nitrate and 17.67 
per cent by water; of the iron 23.85 per cent was leached out by potassium 
nitrate and 7.53 per cent by water; of the manganese 4.76 per cent and 1.19 
per cent were leached out by potassium nitrate and water, respectively. 
Potassium increased 28.95 per cent and nitrate nitrogen 20.69 per cent. 

With the yellow gray silt 99.15 per cent of the acidity was extracted by po- 
tassium nitrate and 7.21 per cent by water; 59.93 per cent of the aluminum was 
leached out by potassium nitrate and 24.73 per cent by water; 14.44 per cent 
of the iron was leached out by potassium nitrate and 2.48 per cent by water; 
and of manganese 3.03 per cent and 1 .03 per cent was leached out by potassium 
nitrate and water, respectively. Potassium was increased 25.72 per cent and 
nitrate nitrogen 55.60 per cent. 

With the yellow silt, potassium nitrate extracted 97.93 per cent of the acidity, 
and water 12.36 per cent; of aluminum 50.61 per cent was leached out by po- 
tassium nitrate and 21.55 percent by water; of iron 21.01 per cent was leached 
out by potassium nitrate and 8.62 per cent by water; of manganese 8.79 per 
cent was extracted by potassium nitrate and 1.51 per cent by water. Potas- 
sium was increased by 28.57 per cent and nitrate nitrogen by 90.47 per cent. 
It may be added that potassium nitrate also leached out some of the calcium 
and phosphorus of the soils. 

Discussion of results. These results reveal the fact that from 44 to 60 per 
cent of the aluminum in the soil may be leached out by potassium nitrate and 
that the leaching of this amount is accompanied by a big decrease in the acid- 
ity. Thus the 44.79 per cent of aluminum leached out from the gray silt was 
accompanied by the disappearance of 96.96 per cent of the acidity. In the 
case of the yellow gray silt the extraction of 59.93 per cent was accompanied 
b}^ the destruction of 99.15 per cent of the aciditj^ With the yellow silt 
50.61 per cent of the aluminum extracted was equivalent to a 97.93 per cent 
decrease in the acidity. It is not to be expected to extract all the aluminum 
in order to reduce the acidity of the soil to zero, for not all the aluminum in the 
soil is in the form readily soluble in potassium-nitrate solution. Some of the 
aluminum is present as silicate and since clay constitutes from 10.15 to 26.4 
per cent of the bulk of the soils under experiment, it is not unlikely that kaolin- 
ite, Al2(OH)4Si206, the chief constituent of clay, is present in considerable 
amounts. Kaolinite is a very stable compound, and although kaolin (70), a 
mechanical mixture of kaolinite and silica, has been found to exchange bases 
with salt solutions, nevertheless, under the conditions in which the aluminum 
has been leached out in the present work, it is not probable that kaolinite and 
allied aluminum minerals will be readily attacked by potassium nitrate solu- 
tions. The case is more likely to be that a considerable amount of soluble 
aluminum compounds — salts and the trihydroxides — are present in the soil. 
In contact with potassium nitrate or even with water these compounds readily 
go into solution and are leached out. The 40 or 60 per cent of aluminum 



184 JOSE JISON MIRASOL 

leached out represents these soluble compounds or acti\e aluminum. This 
active aluminum is equivalent approximately to 53,240 and 90,720 pounds 
per acre, respectively. 

In the case of the water-leached soils it is seen that from 17.67 per cent to 
24.73 per cent of the aluminum is leached out. These percentages are equiv- 
alent approximately to 20,570 pounds and 26,388 pounds per acre, respec- 
tively. The quantity of aluminum found in the water leachings would not 
probably be the actual amount of soluble aluminum in the field because cer- 
tain factors, such as the transporting, storing and drying of the soil when 
brought to the greenhouse, might have contributed to the increase of the solu- 
bility of aluminum, but allowing 50 per cent to these factors we have still 
about 10,000 or 18,000 pounds left to be assigned to the readily soluble alumi- 
num in the soils. The amount of aluminum in the maximum application of 
aluminum nitrate in the sand series is equivalent to 2701 pounds only, and this 
proved fatal to sweet clover. In the normal application of the same salt the 
aluminum is equivalent to 540 pounds per acre only, yet this proved toxic to 
sweet clover. If this is true what a tremendous influence will 10,000 or 18,000 
pounds have on the crop in the field. 

Sweet clover on the leached-ont soils. Sweet clover seeds were sown in both 
potassium-nitrate-leached and water-leached soils. In the case of the former 
there were some difficulties which were never overcome in the case of two 
soils up to the writing up of this work. First, too much potassium nitrate 
was left in the soils in spite of the leaching by water. Gray silt loam had 
28.69 per cent more nitrate nitrogen and 28.95 per cent more potassium than 
the original. Yellow gray silt loam had 55 per cent more nitrate nitrogen, 
and 25.72 per cent more potassium than the original; and the yellow silt had 
90.27 per cent more nitrate nitrogen and 28.57 per cent more potassium. The 
second difficulty was the physical texture of the soils which was badly affected 
by the leaching with potassium nitrate. The soils became more compact 
and sticky. The first planting was consequently a failure. An attempt has 
been made to improve the physical texture of the soil by mixing the soil 
with one-third of its volume of pure silica sand and leaching out with water 
again. But the nitrate remaining was still in large enough amounts to be 
fatal *o seedlings, consequently the second planting was again a failure. The 
soils were laid aside and watered every day until it was thought enough nitrate 
salt had been drained out. Seeds were then planted. At the beginning the 
seedlings seemed to be making headway, but within three weeks the seed- 
lings in the yellow gray and yellow silt loams were already either dead or dying. 
Evidently the concentration of salts in these two tj^ies of soil was still too 
strong for the plants to survive. In the case of the gray silt the seedlings per- 
sisted and grew, although slowly. The growth up to May 19, at the age of 120 
days, is shown in plate 9. A, is water-leached soil, A-1 is polassium-nitrate- 
leached soil, A-2 original soil plus KNO3 equivalent to the e.xcess found in 
the KNOs-leachcd soil plus sand, A-3, the original soil plus sand. Attention 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 185 

is called to the difference of the growth of sweet clover on the different pots. 
The plants in the potassium-nitrate-leached soil, although somewhat stunted 
in growth, were really healthy and deep green. The plants in A-2 and A-3 
were largely chlorotic. This difference in the growth is attributed to the re- 
duction of 96 per cent of the acidity of the soil, which is equivalent to 53,240 
pounds of aluminum removed. It is also important to note the growth of 
sweet clover on the water-leached soil. Although only 96 days old they looked 
just as vigorous as those in the potassium-nitrate-leached soil. This was due 
chiefly to the presence of a still excessive amount of the nitrate salt in the 
potassium-nitrate-leached soil. But it is evident that the removal of about 
20,000 pounds of aluminum by water had greatly benefited the growth of 
sweet clover and this amount was probably the amount of active aluminum 
immediately concerned in the unproductivity of the soils under investigation. 
This effect of the removal of about 44 per cent of aluminum in the soil by po- 
tassium nitrate and 17 per cent by water, on the growth of sweet clover, is 
conclusive proof that aluminum is the chief factor in the unproductivity of 
the three types of soil under investigation and probably of most acid soils in 
America. 

How aluminum salts arise in the soil. The form of aluminum immediately 
concerned in the behaviour of sweet clover toward acid soils is the soluble 
form, the salts. The silicates and hydroxides cannot produce toxicity inas- 
much as they are insoluble in water. In the case of one form of hydroxide, 
the monohydroxide, it has been proven harmless to sweet clover in the present 
investigation. But the salts have been proven injurious to plants even in 
dilute solutions. 

The question now arises as to how aluminum salts may be formed in the 
soil. Aluminum chloride, sulfate and nitrate may all be found in the soil. 
The amount of aluminum chloride will naturally be limited by the absolute 
amount of chlorine in the soil. Aluminum sulfate will also be limited by the 
amount of sulfur. Under certain conditions, if the soil is rich in sulfur and 
the sulfur bacteria are active, through sulfofication considerable amounts of 
aluminum sulfate may be formed. Investigating the effect of sulfofication 
on the availability of potassium in the soil, Ames and Boltz (2) found that 
aluminum was not present in the extract of soils in which sulfur did not enter 
as a part of the treatment, and concluded that aluminum sulfate is formed 
during sulfofication. Artificial treatment of the soil may give rise to consid- 
erable amounts of aluminum sulfate. Ruprecht and Morse (60) found that the 
continuous application of ammonium sulfate to plots in the experimental field 
in Massachusetts produced aluminum sulfate. But great as is the possibility 
of the formation of aluminum sulfate in large quantities, still greater is the 
possibility for the formation of aluminum nitrate. Nitrification is a normal 
process occurring in the soil, and depending on conditions it varies widely. 
At certain seasons of the year nitrification is most active. Such is the condi- 
tion under which large quantities of aluminum nitrate may be formed. In 



186 JOSE JISON MIRASOL 

normal soils, sufficiently provided with limestone, aluminum salt may never 
be formed, but in soils deficient in limestone, aluminum salts are largely formed; 
especially is it true when nitrification is most active. The acid-soluble alumi- 
num trihydroxide in the soil, in the absence of limestone and other suitable 
bases, unites with nitric acid forming aluminum nitrate. The reaction may 
be represented by the following equation: 

A!203.3H«0 + 6HNO3 = 2A1(N03)3 + 6H2O 

If limestone is present in sufficient quantities to satisfy the basic need of nitric 
acid produced, aluminum nitrate and sulfate may never be formed. Calcium 
nitrate, the best form of nitrogen compound for plant-food is formed, instead, 
according to the following reaction: 

CaC03 + HNO3 = Ca(N03)2 + H2O + CO2 

Ames and Boltz (2) noted that the largest amount of aluminum was found in 
solutions from soils where sulfur was oxidized in the absence of calcium car- 
bonate. 

What happens when acid soils are extracted with potassium nitrate before and 
after the application oj limestone. The fact has been repeatedly observed in 
the present investigation that when an acid soil was extracted with potassium 
nitrate the reaction of the extract was always acid, but when limestone (cal- 
cium carbonate) was applied in amounts equivalent to or five times the lime 
requirement, and the soil was extracted with potassium nitrate the reaction 
of the extract was always alkaline and the white gelatinous aluminum hydrox- 
ide precipitate was absent. Knight^ found that "when a base is added to an 
acid soil, comparatively insoluble products are formed. Calcium produces a 
product less soluble than does potassium." Ames and Boltz (2) also found 
that the addition of calcium carbonate at the rate of 80,000 parts per million 
on the soil, decreased the solubility of aluminum to 68 parts per million as com- 
pared with 660 parts per million where calcium was added in amounts just 
sufficient to combine with only a small part of the sulfuric acid. What most 
probably happens is this: When calcium carbonate is applied to the soil, 
calcium bicarbonate is formed which unites with the aluminum salts or with 
the ac'd-soluble hydroxide, forming calcium aluminate, a stable compound. 
The reaction may be written as follows: 

Al2(NO)3.9HiO + 6Ca(HC03)2 = Al203.3CaO + 3Ca(N03)2 + ISHiO 4- 6CO2 



A1;03.3H20 -f 3Ca(HC03)2 = Al:03.3CaO -f 6H2CO3 

When an acid soil comes in contact with potassium nitrate solution an ex- 
change of bases between the soil and the solution takes place (70). The 

• H. G. Knight, "Acidity and .\cidimetrj' of Soil," unpublislied thesis from the University 
of Illinois. 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 187 

aluminum compounds are attacked, bringing aluminum into solution and form- 
ing aluminum nitrate which on hydrolysis produces strong acidity. This is 
the cause of the acid reaction of the solution. When an acid soil is treated 
with calcium carbonate and after a while extracted with potassium nitrate 
the extract is alkaline. An exchange of bases takes place also. But in this 
case the calcium compounds formed in the soil are attacked by the salt solu- 
tion, calcium being replaced by potassium and brought into solution as cal- 
cium nitrate. Such an explanation is in agreement with the findings of van 
Bemmelen (5) and other investigators (70) on the subject of exchange of bases 
between soils and salt solutions, the former having found that when potassium 
chloride solution was added to the soil, almost a complete change of potas- 
sium for calcium and magnesium took place. The presence of calcium ni- 
trate, therefore, which does not hydrolyze, explains the neutral or alkaline 
reaction of the extract. 

Experiment IV. Iron and manganese as factors in soil acidity 

The table of analysis reveals that the types of soil under investigation also 
contain considerable quantities of iron and manganese. The gray silt contains 
47,800 pounds of iron and 840 pounds of manganese per acre. The yellow 
gray silt contains 40,300 pounds of iron and 786 pounds of manganese per 
acre; and the yellow silt contains 74,200 pounds of iron and 660 pounds of 
manganese per acre. The toxicity of normal iron salts at a certain concentra- 
tion is well known, and Ruprecht and Morse (61) found that in the unproduc- 
tivity of ammonium-sulfate fertilized plots of the Massachusetts Agricultural 
Experiment Station, ferric and manganese salts were also contributing factors. 
Funchess (20) also observed that in Alabama the development of soluble 
manganese salts was the cause of the unproductivity of a certain soil. The 
question now comes up as to whether iron and manganese might not be also 
contributing factors in the acidity of the soils under investigation. It was 
thought that if these metals were as important a factor as aluminum, some 
idea might be obtained from their degree of solubility and their ratio to soluble 
aluminum. Fortunately, the first 4-liter potassium-nitrate leachings of the 
gray silt and the first 4-liter water-leachings of the three tjqses of soil have been 
saved. These leachings were analyzed for aluminum, iron and manganese. 
The results of the analysis are given in table 9. 

This table shows that the ratio of aluminum, iron and manganese in the first 
4 liters of the potassium-nitrate leachings is 4.6:1:1.2. The first 4 liters of 
water extract gave for the gray silt loam 4.8 for aluminum, 1 for iron and 1.1 
for manganese; for the yellow gray silt loam 6.2 for aluminum, 1 for iron and 
1.3 for manganese; and for the yellow silt 3.4 for aluminum, 1 for iron and 1.7 
for manganese. The proportion of aluminum to iron or manganese is such that 
there can be no doubt that aluminum is the dominant factor. In the case of 
manganese a further step has been taken. Sand-culture experiments were 

SOIL SCIENCE, VOL. X, NO. 3 



188 



JOSE JISON MIRASOL 



carried out with manganese sulfate, nitrate and carbonate, the plan being the 
same as that in the aluminum series. The results of these experiments reveal 
that manganese cannot be any factor in the soil in question for this reason. 
When calcium carbonate in considerable quantities was combined with alumi- 
num salts the toxicity of the aluminum was corrected. In the case of the 
soils, calcium carbonate also corrected their acidity or unproduclivity, but 
with manganese compounds not even the application of five times the lime 
requirement of calcium carbonate has corrected the toxicity of manganese. 
It is not denied that iron and manganese might become factors in the acidity 
of some soils but with the soils under investigation there is no doubt that 
aluminum is the determining factor in their acidity. 

TABLE 9 
A nalysis of extracts (4 liters) 



TYPE OF SOIL 



Gray silt (mgm.) 

Ratio 

Gray silt (mgm.) 

: Ratio 

YdUow gray silt (mgm.) 
• Ratio 

Vellow silt (mgm.) 

Ratio 



DETEKIOKEO 



Aluminum 


Iron 


Manganese 


KNOi extract 


282. S 
4.6 


60.9 
1 


49.8 
1.2 


HtO extract 



75.5 
4.8 



105.2 
6.2 



88.9 
3.4 



15.8 
1 



17.0 
1 



26.3 
1 



14.6 
1.1 



13.1 
1.3 



16.3 
1.7 



V. SUMMARY 



Experiments have been carried out, first, to find out the influence of alumi- 
num salts and aluminum hydroxide, alone and in combination with calcium 
carbonate or with acid phosphate, on the growth of sweet clover grown in 
sand; second, to determine the effect of limestone and acid phosphate alone 
and in combination, on the productivity and acidity of three types of silt loam 
Soil; third, to find out the effect of the removal of some aluminum from the 
Soil on the growth of sweet clover; and fourth, to ascertain whether iron and 
manganese also are factors in the acidity of the soils under investigation. 

In the absence of some calcium compounds as a source of calcium, aluminum 
salts were highly to.xic to sweet clover when applied in amounts chemically 
equivalent to the acidity of the soil, and fatal to sweet clover when applied in 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 189 

amounts chemically equivalent to five times the acidity of the soil. In the 
presence of calcium silicate, aluminum nitrate was more toxic than aluminum 
suKate. 

Aluminum mono-hydroxide had no effect whatever on the growth of sweet 
clover, when other plant-food elements were added in water-soluble form. 

Calcium carbonate in sufficient amounts corrected the toxicity of aluminum 
salts, by precipitating aluminum as calcium aluminate, an insoluble compound. 

Acid phosphate applied at the rate of 400 pounds per acre reduced the tox- 
icity of aluminum salts by formingaluminum phosphate, an insoluble aluminum 
compound. 

Limestone applied at a rate equal to the lime requirement produced good 
crops on the three silt loam soils; applied at the rate of five times the lime re- 
quirement it produced better crops. At the same rate of application the soils 
were alkaline at the end of 178 days. The action of calcium carbonate in 
the soil is to unite with the aluminum salts and the acid-soluble aluminum 
hydroxide, forming calcium aluminate. 

Acid phosphate applied alone at the rate of 1 ton to the acre produced fair 
crops, at the rate of 5 tons good crops. Acid phosphate also reduced the acid- 
ity of the soils and the decreases depended on the rate of application. At the 
rate of 5 tons per acre acid phosphate reduced the acidity of the soils from 51 
to 57 per cent. The reduction of the acidity was due to the formation of the 
insoluble aluminum phosphate. 

The combination of acid phosphate and limestone in large quantities pro- 
duced the best crops. 

The aluminum in the soil varies from 121,000 to 151,000 pounds per acre. 
When the soil was leached out with potassium nitrate solution until the last 
125 cc. of leachings was practically neutral, the acidity of the soil was reduced 
99 per cent and as much as 59 per cent of the aluminum was leached out. 
Sweet clover growing on leached soil was better than that growing on un- 
leached soil. The fact conclusively proved that aluminum is the determining 
factor in the acidity of the soils under investigation and probably of most 
other acid soils of the same origin. 

The form of aluminum immediately concerned in the unproductivity of acid 
soils in the soluble form, is the salts. These salts are derived from the acid- 
soluble aluminum hydroxide, or gibbsite. In soils sufficiently provided with 
calcium, toxic aluminum salts may never be formed, but in soils deficient in 
calcium and other bases, as in the case of acid soils, toxic aluminum salts are 
largely the end-products of sulfofication and nitrification. 

It is not denied that iron and manganese may become contributing factors 
in the unproductivity of some acid soils, but the preponderance of evidence 
points to aluminum as the determining factor in the acidity of the soils under 
investigation. 

The potassium nitrate extract of an acid soil is acid, but the same extract 
after sufficient amounts of limestone have been applied to the soil is alkaline. 



190 JOSE JISON MIRASOL 

In the first case an exchange of bases lakes place between the aluminum com- 
pounds and the potassium-nitrate solution bringing aluminum into solution 
and forming aluminum nitrate, which on hydrolysis produces strong acidity. 
This is the cause of the acid reaction of the solution. In the second case an 
exchange of bases also takes place, but this time between the calcium com- 
pounds and the potassium nitrate solution, bringing calcium into solution and 
forming calcium nitrate. This compound is not hydrolyzed and therefore 
will not produce acidity. This explains the neutral or alkaline reaction of the 
extract. 

In so far as aluminum is a factor in soil acidity the Hopkins method is the 
best one for soil-acidity determinations. It determines active aluminum and 
under field conditions when the lime requirement of the soil has been satisfied 
with the amount of calcium carbonate as determined by the method, the tox- 
icity of aluminum is eliminated. 

.\CK\OWLEDGMEXT 

The author desires to express his obligations to Prof. Robert Stewart for 
his valuable suggestions and criticisms during the progress of the investigation; 
to Prof. Charles F. Hottes for suggestions on the experiment on the toxicity 
of aluminum salts in water culture; to Prof. Cullen W. Parmelee for informa- 
tion on the constitution of aluminum compounds in the soil; to Dr. Raymond 
S. Smith, under whom the mechanical analysis of the soils was made; to Dr. E. 
De Turk for reading the manuscript and to Messrs. J. C. Anderson and W. 
Green for help rendered in the preparation of pot cultures. 

REFERENCES 

(1) Abbott, J. B., Coxner, S. D., and Smalley, H. R. 1913 Soil acidity, nilrification 

and the toxicity of soluble salts of alummum. Ind. (Purdue Univ.) Agr. Exp. 
Sta. Bui. 170. 

(2) Ames, J. W., and Boltz, G. E. 1917 Effect of sulfofication on potassium and other 

soil constituents. In Soil Sci., v. 7, no. 3, p. 183-195. 

(3) Ames, J. \V., and Schollenberger, C. J. 1916 Liming and lime requirement of 

soil. Ohio Agr. Exp. Sta. Bui. 306. 

(4) Baguley, a. 1912 The phosphate nutrition of plants. In Jour. .\gr. Sci., v. 4, pt. 

33, p. 318-322. 

(5) Bemtsjelen, J. M., van 1878 Das Absorptionwermogender Ackerde. In Landw. 

Vers. Stat., Bd. 21, p. 135. 

(6) BERZELI0S, Jons Jacob 1856 Lehrbuch der Chemie, Bd. 3, Aufl. 8, p. 389. Leipzig. 

(7) Beyer, S. W., and Williams, I. A. 1903 Technology of clays. In Iowa Geol. 

Survey Ann. Rpt. 1903, v. 14, p. 29-318. 

(8) Blair, A. W., and Macy, E. J. 1908 Acid soils. Fla. .'Vgr. Exp. Sta. Bui. 93. 

(9) BouLLANGER, E. 1912 Etudcs exp6rimentales sur les engrais catalytiques. In 

Ann. Sci. Agron., ser. 4, t. 1, no. 3, p. 161-180. 
(10) BuRD, J. S. 1918 Chemical criteria, crop production and physical classification in 
two soil classes. In Soil Sci., v. 5, no. 5, p. 405. 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 191 

11) Cameron, F. K., and Bell, James M. 1905 The mineral constituents of the soil 

solution. U. S. Dept. Agr. Bur. Soils Bui. 30. 

12) Clark, F. W. 1916 The data of geochemistry. U. S. Geol. Survey Bui. 616, .3rd ed., 

p. 34. 

13) Conner, S. D. 1916 Acid soils and the effect of acid phosphate and other fertilizers 

upon them. In Jour. Indus. Engin. Chem., v. 8, no. 1, p. 3.S. 

14) Daikl-hara, G. 1914 Ueber saurelMineralboden. In Bui. Imp. Cent. Agr. Exp. 

Sta. Japan, v. 2, no. 1, p. 1-41. 

15) Edwards, M. G. 1914 The occurrence of aluminum hydrates in clays. In Econ. 

Geol., V. 9, p. 117. 

16) EiCHHORN, Prof. 1877 Ueber die Einwirkung humus reicher erden auf Salze, be- 

sonder Phosphorasauren Kalk. In Landw. Jahrb., Bd. 1, p. 957. 

17) Failyer, G. H., Smith, J. G., and Wade, H. 1908 The mineral composition of 

soil particles. U. S. Dept. Agr. Bur. Soils Bui. 54. 

18) Flusi, M. 1908 Der Einfluss von Aluminum salzen auf das Protoplasma. In Flora, 

Bd. 99, No. 2, p. 81-126. 

19) Frear, W. 1915 Sour soils and liming. Com. Penn. Dept. Agr. Bui. 261. 

20) FdnCHEss, M. J. 1918 The development of soluble manganese in acid soils as influ- 
enced by certain nitrogenous fertilizers. Ala. Agr. E.xp. Sta. Bui. 201 (Tech. 
Bui. 4). 

21) Galpin, S. L. 1912 Studies of flint clays and their associates. In Trans. Amer. 
Ceram. Soc, v. 14, p. 301. 

22) Gillespie, L. J. 1916 The reaction of soil and soil measurement of hydrogen-ion 
concentration. In Proc. Wash. Acad. Sci., v. 6, no. 1, p. 7-16. 

23) GuLLEY, A. 1915 Humus acids in the light of the results of recent investigation. 
In Intemat. Mitt. Bodenk., Bd. 5, No. 3, p. 232-247; No. 4, p. 347-368; Abs. in 
Exp. Sta. Rec, v. 35, p. 628. 

24) Hall, A. D., and GnaNOHAM, C. T. 1907 The interaction of ammonium salts and 
the constituents of the soil. In Jour. Chem. Soc. (London), v. 91, pt. 1, p. 677. 

25) Harris, J. E. 1914 Soil acidity. Mich. Agr. Exp. Sta. Tech. Bui. 19. 

^26) Harris, J. E. 1914 Some adsorption phenomena in soils and kaolin. In Jour. Phys. 

Chem., v. 19, p. 355. 
]27) Hartwell, B. L., and Pember, F. R. 1918 The presence of aluminum as a reason 

for the difference in the effect of so-called acid soils on barley and rye. In Soil 

Sci., v. 6, no. 4, p. 259. 

28) Hartwell, B. L., AND Pember, F. R. 1919 Lime requirements as determined by the 

plant and by the chemist. In Soil Sci., v. 7, no. 4, p. 279. 

29) Hebert, a. 1907 Toxicite des sels de chrome d'aluminum et de magnesium; leur 

action sur deverses fermentations. Comparaison avec les proprietes analogues 
des terres rares. In Bui. Soc. Chim. Paris, ser. 4, no. 1, p. 1026-1032. 

30) HiLGARD, E. W. 1914 Soils, p. 389. Macmillan Co., New York. 

31) Hillebrand, W. F. 1905 The analysis of silicate and carbonate rocks. U. S. Geol. 
Survey Bui. 305, Ser. E. 

32) Hopkins, C. G. 1910 Soil Fertility and Permanent Agriculture. Ginn and Co., 
New York. 

33) Hopkins, C. G., Knox, W. H., and Pettit, J. H. 1903 A quantitative method for 
determining the acidity of soils. U. S. Dept. .A.gr. Bur. Chem. Bui. 73, p. 114. 

34) Hopkins, C. G., and Pettit, J. H. 1910 Soil Fertility Laboratory Manual. Ginn 
and Co., New York. 

35) House, H. D., and Gies, W. J. 1905-1906 The influence of aluminum ions on lupine 

seedlings. In Amer. Jour. Physiol., v. 15, p. 19. 

36) Hunt, T. F. 1909 Soil fertility. Penn. Agr. Exp. Sta. Bui. 90. 

37) Johnson, S. W. 1913 How Crops Grow. Orange Judd Co., New York. 



192 JOSE JISON MIRASOL 

(38: 



(39: 
(4o: 

(41 
(42 

(43 

(44: 
(45: 
(46: 

(47 

(48: 
(49: 
(5o: 

(51 
(52 

(53: 

(54: 
(55: 

(56: 

(57: 

(58 
(59 

(6o: 

(61 
(62 

(63: 



JosT, L. 1907 Plant Physiology. Translation by R. J. Han'cy Gibson, p. 86. 

Clarendon Press, Oxford. 
Kkatemann, E. 1914 The physiological action of the salts of aluminum upon plants. 

In Sitzber. K. .\kad. Wiss. [Vienna], Math. Naturw. Kl., Bd. 123, II, III, p. 211- 

233; Abs. in E.\p. Sta. Rec, v. 34, p. 525. 
LiNDGREN, W. 1913 Mineral Deposits, p. 326. New York. 
LoEW, O. 1913 Studies on acid soils of Porto Rico. Porto Rico Agr. Exp. Sta. 

Bui. 13. 
Lyman, J. B., Martin, F. O., and Pearce, J. R. 1914 The centrifugal method of 

mechanical soil analysis. U. S. Dept. Agr. Bur. Soils Bui. 24. See also Bui. 

84 of the same bureau. 
Maze, P. 1915 Determination des elements mineraux rares necessaires an developpe- 

ment du mais. In Compt. Rend. Acad. Sci. (Paris), t. 160, p. 211-214. 
Myers, C. N. 1914 Soluble aluminum compounds — their occurrence in certain 

vegetable products. In U. S. Publ. Health Rpt., v. 29, no. 25, p. 1625-1629. 
Micheels, H., .vnd DeHeen, P. 1905 Note an sujet de Taction des sels d'aluminum 

sur la germination. In Bui. Acad. Roy. Belg., (1905), p. 520. 
MiYAXE, K. 1916 The toxic action of soluble aluminum salts upon the growth of 

the rice plant. In Jour. Biol. Chem., v. 25, p. 23. 
Munerati, O., Mezzadroli, G., and Z.^pparoli, T. V. 1913 Influence of certain 

stimulants on the development of sugar beets. In Staz. Sper. Agr. Ital., v. 46, 

no. 7-8. p. 486-498; Abs. in Exp. Sta. Rec, v. 31, p. 233. 
Olsen, J. C. 1918 Physical constants of inorganic compounds. In Van Nostrand's 

Chemical .\nnual. Fourth Issue, p. 130. New York. 
Parker, E. G. 1914 Selective adsorption. In Jour. Indus. Engin. Chem., v. 6, p. 

831. 
Ppeffer, W. 1899 Physiology of Plants. Translation by A. J. Ewart, v. 1, p. 437. 

Clarendon Press, O.xford. 
Pi'Eii'rER,TH., .-vNo Blank. 1913 Beitrag zur Frage uber die Wirkung des Mangans 

bezw. aluminums auf Pflanzen-wachstum. In Landw. Vers. Stat., Bd. 83, 

No. 3-4, p. 257-281. 
PrianisCHNIkov, D. 1911 Uber der Einfluss von kohlen-sauren Kalk auf die Wirkung 

von verschiedenen Phosphaten. In Landw. Vers. Stat., Bd. 75, No. 5-6, p. 357. 
Richards, J. W. 1890 .\luininum: Its History, Occurrence, Properties, Metallurgy 

and Applications, Including its .-Mloys; 2nd ed., p. 46. Laird and Lee, Chicago. 
RiES, H. 1914 CKiys, their Occurrence, Properties and Uses; 2nd ed., p. 202. 
Robinson, \V. O. 1914 The inorganic composition of some important American 

soils. U. S. Dept. Agr. Bui. 122. 
Robinson, W. O., Steinkoenig, L. A., and Fry, W. H. 1917 Variation in the 

chemical composition of soils. U. S. Dept. Agr. Bui. 551. 
Robinson, W. O., Steinkoenig, L. N., and Miller, C. F. 1917 The relation of 

some of the rarer elements in soils and plants. U. S. Dept. Agr. Bui. 600. 
Rolfe, C. W. Geology of Clays. 111. Geol. Surv. Bui. 9. 
RupRECHT, R. W. 1915 Toxic efifect of iron and aluminum salts on clover seedlings. 

Mass. Agr. E.xp. Sta. Bui. 161. 
RtrPRECHT, R. W., AND MoRSE, F. W. 1915 The effect of sulfate of ammonia on 

soil. Mass. Agr. Exp. Sta. Bui. 165. 
RopRECHT, R. W., AND MoRSE, F. W. 1917 The cause of the injurious effect of 

sulfate of ammonia when used as a fertilizer. Mass. .\gr. Exp. Sta. Bui. 176. 
Sharp, L. T., and Hoaci.and, D. R. 1915 Acidity and adsorption in soils as meas- 
ured by the hydrogen electrode. In Jour. Agr. Res., v. 7, p. 123-145. 
Shorey, E. C. 1912 Some constituents of humus. In Proc. Internal. Cong. Appl. 

Chem., v. 15, p. 247-252. 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 193 

SoLENOW, N. 1909 Die Boden aciditat und ihre Bedeutung fur den Kulturboden. 

Inaug. Dissert, Jena. (Original article not seen.) 
Sprenger, C. 1826 Ueber Pflanzenhumus, Humussaiire und humussaure Salze. In 

Kastner Arch. Gesam. Naturl. Niirnberg, Bd. 8, p. 145-220. (Original article 

not seen.) 
Steinkoenig, L. a. 1915 Distribution of certain constituents in the separates of 

loam soils. In Jour. Indus. Engin. Chem., v. 6, no. 7, p. 576. 
Stoddart, C. W. 1916 Chemistry of Agricultur, p. 242. Lea and Febiger, New 

York. 
Stoklasa, J. 1911 Catalytic fertilizers for sugar beets. In Bl. Zuckerriihenbau, 

Bd. 18, No. 11, p. 193-197; Ahs. in Exp. Sta. Rec, v. 26, p. 225. 
Storer, F. H. 1899 Agriculture, v. 2, p. 214-15. Scribner and Sons, New York. 
Sullivan, E. C. 1907 The interaction between minerals and water solutions. U. S. 

Geol. Survey Bui. il2. 
Tacke, Br., and StJCHTiNC, H. 1911 Ueber Humussauren. In Landw. Jahrb., 

Bd. 41, p. 717. 
Thorne, C. E. 1909 Carriers of phosphorus in fertilizers. Ohio Agr. Exp. Sta. Cir. 

93. 
Tread^vell, F. p. Analytical Chemistry. Translation by Hall, W. T., 4th ed., v. 2, 

p. 126, 150. Wiley and Sons, New York. 
Truog, E. 1913 Availability of phosphate to various crops. In Wis. Agr. E.xp. 

Sta. Bui. 240, p. 22. 
Truog, E. 1915 Soil acidity and methods for its detection. In Science, v. 42, p. 

505. 
Truog, E. 1916 The utilization of phosphate by agricultural crops, including a 

new theory regarding the feeding power of plants. Wis. Agr. Exp. Sta. Res. 

Bui. 41. 
Truog, E. 1916 The cause and nature of soil acidity with special regard to colloids 

and adsorption. In Jour. Phys. Chem., v. 20, no. 6, p. 457. 
Van Slyke, L. L. 1919 Fertilizers and Crops, p. 112. Orange Judd Co., New 

York. 
Varvaro, U. 1912 The action of manganese dioxide and other metallic compounds 

on the germination of seed. In Staz. Sper. Agr. Ital., v. 45, no. 12, p. 917-929; 

Abs. in Exp. Sta. Rec, v. 29, p. 528. 
Veitch, F. p. 1904 Comparison of methods for the estimation of soil acidity. In 

Jour. Amer. Chem. Soc, v. 10, p. 637. 
VoELCKER, J. A. 1909 Pot culture experiments. In Jour. Roy. Agr. Soc. England, 

v. 70, p. 394. 
Wheeler, H. J. 1913 Manures and Fertilizers, p. 216. Macmillan Co., New 

York. 
Wheeler, H. J., and Towar, J. B. 1893 On the occasional ill-effect of sulfate of 

ammonia as a manure and the use of air-slacked lime in overcoming the same. 

In Ann. Rpt. R. I. Agr. Exp. Sta., v. 6, p. 206. 
Yamano, G. 1905 Can aluminum salts enhance plant growth? In Bui. Col. Agr., 

Tokyo Imp. Univ., v. 6, no. 4, p. 429^32. 



PLATE 1 
Effect op Aluminum Sulfate on the Growth of Swtet Clo\t:r 

Fig. 1. First crop, 93 days old. 
101 — Control — plant-food only. 

102 — Plant-food plus 3100 pounds of Al2(SOi)3 per acre. 
103 — Plant-food plus 620 pounds of Alj(SOi)3 per acre. 
lOi — Plant-food plus 1,S,500 pounds of Al2(S04)3 per acre. 

105 — Plant-food plus 3100 pounds of Al2(S04)3 per acre plus 2716 pounds of CaCOj. 
106 — Plant-food plus 3100 pounds of Ali(S0<)3 per acre plus 543 pounds of CaCOa. 
107— Plant-food plus 3100 pounds of Alj(S0<)3 plus 13,580 pounds of CaCOa. 
108 — Plant-food plus 3100 pounds of .\l2(S04)3 per acre plus 1054 jxjunds of CaC03. 
109 — Plant-food plus 3100 pounds of .\l2(S04)3 per acre plus 211 pounds of CaCOs. 
110 — Plant-food plus 3100 pounds of Al2(SOi)3 per acre plus 5270 pounds of CaCOs. 
Fig. 2. Second crop, 96 days old. The same as above plus CaSi03 and acid phosphate, 
reduced from 100 to 400 pounds per acre. 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 

JOSE JISON UIHASOL 





. SCIENCE. VOL, 10, NO. 3 



PLATE 2 

ICfFKCT of ALUMIXUII Cill.ORIDE ON SwEET ClO\"ER 

I- Id. 1. Sweet clover at tlie ai;e of 44 clays. 

201— Control— Planl-food only. 

202— Plant-food plus 2405 poimtls of.MClj per acre. 

203— Plant-food plus 461 pounds of .-MCU per acre. 

204— Plant-food plus 12,025 pounds of .\ICI3 per acre. 

205— Plant-food plus 2405 pounds of AICI3 plus 2716 pounds of CaCOa per acre. 

206— Plant-food plus 2405 pounds of .AIClj plus 543 pounds of CaCOa per acre. 

207— Plant-food plus 2405 pounds of AICI3 plus 13.580 pounds of CaCOa per acre. 

208— Plant-food plus 2405 pounds of AlClj plus 1054 pounds of CaH,(P04)2 per acre. 

209— Plant-food plus 2405 pounds of .UCL, plus 211 pounds of CaH4(P04)2 per acre. 

210— Plant-food plus 2405 pounds of Aid,, plus 5270 pounds of CaHifPOOj per acre. 

Fic. 2. Same, at the ago of 93 day.;. Treatment, same as above. 



196 



ALUMINUM AS A FACTOR IN SOIL ACIDITV 

JCSK JI50N ; 










< 
































^^&., ,i 


^1 


fc 






■4^ 






fl^H 


M 






Toi 1 




1 to* 


fr\ 


noT 


y 




Ulfl 



W7 



Effect •)F Alumivuu \itrate ov Sweet Clover 

KiG. I. First crop, 93 days old. 

301 — Control— Plant-food only. 

302— Plant-food plus 3S59 p'.unds of Al(XO:,)3 gH/J per acre. 

303— Plant-food plus 752 pjunds of .\.UN'03)3.9H20 per acre. 

304— Plant-food plus 19,295 pounds of AUXOa), 9H2O per acre. 

305— Phnt-food plus 3^59 pounds of A1(N'03)3 9H2O plus 2716 pounds CaCOj per acre. 

306— Plant-food plus 3S59 pounds of A1(X03)3.9H20 plus 5i3 pounds of CaCOj per acre. 

307— Plant-food plus 3vS9 pounds of A1(N'03)3 9HoOplus 13,580 pounds of CaCOj per acre. 

30S— Plant-food plus 3H.S9 pounds of Al(.\0,)3 9H;0 plus 1054 pounds of CaH4(POj)2per 
acre. 

309— Plant-food plus 3^59 pounds of AKXOj^j 9H2O plus 211 pounds of CaH,(P04)2 per 
acre. 

310— Plant-food plus 3859 pounds of AU.XOj), 9H2O plus 5270 pounds of CaH4(POi)2 per 
acre. 

Fig. 2. Second crop, 96 diys old. Same as above with the same changes as noted in 
scries 100. 



193 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 

JOSE IISON UIR,\SOL 





T' -'^'" 


5iv 






n^Tl 


1 tn-S 1 ^ ;!„:, f ;,„j » ,,„j M ,^^ 




Effect of Alcminum Hydroxide on Sweet Clove;; 

Fig. 1. First crop. 93 days old. 

401— Control— Plant-food only. 

402— Plant-food plus I.IW pounds of AU0H)3 per acre. 

403— Plant-food plus 2>;0 jjounds of .Vi;0H)3 per acre. 

404— Plant-food plus 6W.=; pounds of AllOHjj per acre. 

405— Plant-food plus 13W pounds of AUOH), [)lus 2716 pounds of CaCOj per acre. 

406— Plant-fooil plus 1399 pounds of AUOIDa plus 543 pounds of CaCO,, per acre. 

407— Plant-food plus 1399 pounds of Al(OH)., plus 13„SS0 pounds of CaCOj per acre. 

40.S— Plant-food plus l.?99 pounds of .\l(OH), plus 10.=;4 pounds of CaH^lPOi)-; per acre. 

409— Plant-food plus 1399 pounds of .\l(OH),, plus 211 pounds of CaH,(POj), per acre. 

410— Plant-food plus 1399 pounds of Al(OH).i plus 5270 pounds of CaHiCPOj): per acre. 

Fig. 2 -3. Second crop. 96 days old. Same as above up to 410 with the same changes as 
noted in series 100 to 300. 

411— Plant-food plus 1399 pounds of AliOH),, plus 800 pounds of (XH,).SO, per acre. 

412— Plant-food plus 1399 pounds of Al(OH)3 plus 160 pounds of (NHOsSO, per acre. 

413— Plant-food plus 1.599 pounds of Al(OH)3 plus 4000 pounds of (NHij.SO., per acre. 

414— Plant-food plus 6995 pounds of .'\l(OH)c plus 800 pounds of (XH4)2S04 per acre. 

415— Plant-food plus 1399 pounds of A1(()H), plus 800 pounds of (XIl4):S0i plus 2716 
pounds of CaCOa per acre. 

416— Plant-food plus 1599 pounds of AU0H)3 plus SOO pounds of (XHiJiSOj plus 543 
pounds of CaCOs per acre. 

417- Plant-food plus 1399 jMurnds of .VKOHIs plus 800 pounds of (XHil.SOj plus 13.580 
pounds of CaCOa per acre. 

418— Plant-food plus 1399 pounds of .^liOIDs plus 2423 pounds of dried blood per acre. 

419— Plant-food plus 1.599 pounds of .M'OHU plus 484 pciunds of dried blood per acre. 



ALIMINL'M AS A FACTOR IN SOIL ACIDITY 

JObE JISON MIR-ASON 






Fic. 3 
201 



Effect of Acid Phosphate on- Sweet Clovek 

Imc. 1. First crop, 75 days old. 
601 — Control — I'lant-food only. 
■ 602— Plant-food plus 964 pounds of CaHjIPO,)^ per acre. 
60.?— Phnt-food plus 19.S pounds of CaH4(POi)3 per acre. 
6(M— Plant-food phis 4^20 pounds of CaH4(P04)3 per acre. 

605— Plant-food plus %4 pounds of CaH4(P04)3 plus 2921 pounds of CaCOj per acre. 
606 — Plant-food plus 961 pounds of CaH4(P04).i plus 5.S4 pounds of CaCOs per acre. 
607— Plant-food plus 964 pounds of CaH4(P04)3 plus 14635 pounds of CaCOs per acre. 
Fig. 2. Second crop. 67 days old. Amounts of acid phospliatc reduced to from 100 to 
400 pounds per acre. 



202 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 

JOSE JISON MIRASOL 




Fig. 1 



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203 



Effect of I.imintonf. axd Acid Pikispii atk dn: the PRiiuiCTiviTV of C.kw Silt I.oam 

Fig. 1. First crop, 98 d:us old. 

701— Control. 

702 — 2125 pounds of limestone per acre. 

703 — 425 pounds of limestone per acre. 

704 — 10,625 pounds of limestone per acre. 

705—2310 pounds of CaH4(POj)2 per acre. 

706—462 pounds of CaH4(P04)i per acre. 

707—11,550 pounds of CaH,(P04): per acre. 

70iS — 2310 pounds of CaHjfPOi): plus 2125 [)Ounds of limestone per acre. 

70y — 2310 pounds of CaH4(P04)2 plus 425 pounds of limestone per acre. 

710 — 2310 pounds of CaHi(P04)2 plus 10.625 p-iunds of limestone per acre. 

Fig. 2. Second crop, 123 days old. Treiitment, same as above. 



204 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 

JOSE JISON MIHASOL 



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205 



l'"['Fr.CT OF Limestone and Acid Phosphate on the Productivity or ^■ELL0U• Gray Silt 

Loam 

Fig. 1. First ( r()[>, 98 days cild. 

801— Contrcl. 

802 — 2813 pounds of limestone per acre. 

803 — 5(>2 pounds of limestone per acrc- 

804 — 14,065 pounds of limestone per acre 

805—3080 pounds of CaH,(P0i)2 per acre. 

S06 — 616 pounds of CaH4(POi)2 per acre. 

807—15,400 pounds of CaH^fPOj » per acre. 

808—3080 pounds of CaH4(P04)2 plus 2813 pounds of limestone per acre. 

800 — 3080 pounds of CaH<(P04)2 plus 562 pounds of limestone per acre. 

810 — 30-0 pounds of CaHjfPOj):; plus 14.065 pounds of limestone per acre. 

I'iG. 2. Second crop, 123 day? old. Treatment, same as above. 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 

JOSE JISON MIBASOL 





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Effect of Limestone and Acid I'uosphate ov the Prodixti\itv of \'ello\v Silt Loam 

Fig. 1. First cmp, 9S days old. 

901— Control. 

902 — 2921 pounds of limestone per :icre. 

903 — 5S4 pounds of limestone per acre. 

90i — 14.605 pounds of limestone per acre. 

905—3080 pounds of CaHj(P0i1; per acre. 

906—616 pounds of CaH4(P04'l2 per acre. 

907—15,400 pounds of CaH^d'O,)^ per acre. 

90S— 3080 pounds of CaH4fP04)2 plus 2921 pounds of limestone per acre. 

909— .SOSO pounds of CaHi(P04)2 plus 584 pounds of limestone per acre. 

910— 30S0 pounds of CaH4(P04)2 plus 14.605 pounds of limestone per acre. 

Fm. 2. Second crop, 123 days old. Treatment, same as above. 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 

JOSE JISON MIRASOL 




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209 



PLATE 9 
S\VEr;T Clover on Potassium-Nitrate and Water-Leached Gray Silt Loam Soil 

A. Water-leached soil. 

A-1. Potassium-nitrate-leaclied soil. 

A-2. Original soil plus KNO3 equal to excess of KXO3 in .'\-l. 

A-3. Original soil. 



210 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 

JOSE JISON MIRASOL 




CfR.'vphs Showino the Decrease of Acidity of Soil Dl^e to Treatment — Gray 
Silt Lo.\ii 

Curve 1 represents the [)cr cent decrease of acidity in 108 days; curve 2 the per cent de- 
crease in 17S days. 
701— Control 

702 — 2125 pounds of limestone per acre. 
703 — 42.5 pounds of limestone per acre. 
704 — 10,625 pounds of limestone per acre. 
705 — 2310 pounds of CaH4(POi)2 per acre. 
706 — 462 pounds of CaH4fP04)2 per acre. 
707 — 11,550 pounds of CaH4(P04)2 per acre. 

708—2310 pounds of CaH4(P04)2 plus 2125 pounds of limestone per acre. 
709 — 2310 pounds of CaH4(P04)2 plus 425 pounds of limestone per acre. 
710—2310 pounds of CaH4(P04)2 plus 10,625 pounds of limestone per acre. 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 

JOSE JISON MIKASOI, 



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213 



Graphs Showint. the Df.ciceasf. of Acidity of Soil Due to Treatment — Vei.i.ow 
Gray Silt Lo.ym 

Curve 1 represents the per cent decrease of acidity in lOS days; curve 2 the per cent 
decrease of acidity in 178 days. 
801— Control. 

802 — 2813 pounds of limestone per acre. 
803 — 562 pounds of limestone per acre. 
804 — 14,065 pounds of limestone per acre. 
805—3080 pounds of CaHiCPOi), per acre. 
806 — 616 pounds of CaHi(P04)2 per acre. 
807—15,400 pounds of CaH/PO,): per acre. 

808 — 3080 pounds of CaHi(P04)2 plus 2813 pounds of limestone per acre. 
809 — 30S0 pounds of CaHjfPOi)* plus 562 pounds of limestone per acre. 
810 — 3080 pounds of CaH4(P04)2 plus 14,065 pounds of limestone per acre. 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 

jOSE JISON MIRASOL 



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C.KAi-iis Showing the Decreask of Acidity of Soil Die to Treatment — Yellow 
Silt Loam 

Curve 1 represents the per cent decrease of acidity in lOS days; curve 2 the per cent 
<iecrease of acidity in 1 78 days. 
90! -Cuntrol. 

902 — 2921 pounds of limestone per acre. 
903 — 5K4 pounds of limestone per acre. 
904— 14.60.> pounds of limestone per acre. 
90.S- ,W0 pounds of CaHitPOvj per acre. 
906-616 pounds of CaHji POj)-: per acre. 
907—1.^.400 pounds of CaHifP04>2 per acre. 

90K— 30S0 pounds of CaHi(PO,).. plus 2921 ])ounds of limestone per acre. 
909— .SOSO pounds of CaH4(P04)2 plus 594 pounds of limestone per acre. 
910—3080 pounds of CaHj(P04)o plus 14,60.i pounds of limestone per acre. 



ALUMINUM AS A FACTOR IN SOIL ACIDITY 

JOSE JISON MIRASOL 




Ser.t! .Is 9^/ ^^ ^ 



VITA 

The author of this thesis was born in the town of Silay, province of Occi- 
dental Negros, Philippine Islands, April 19, 1891. He began his education in 
the private schools of the same town and in 1903 entered the public schools of 
Occidental Negros. From 1903 to 1907 he attended the primary and inter- 
mediate schools of Silay, and from 1907 to 1912 the intermediate and high 
schools of Occidental Negros, at Bacolod. Aftergraduationin 1912 he entered 
the University of the Philippines as a provincial government student of Occi- 
dental Negros, graduating therefrom with the degree of Bachelor of Science in 
Agriculture, in 1915. His graduating thesis was: "Chemical Changes during 
the Ripening of Sugar Cane." He received the Master of Science degree in 
1917, having as his thesis, "Spacing and Fertilizer Tests with Sugar Cane." 
From July, 1915 to February, 1916 he was employed in the College of Agricul- 
ture, University of the Philippines as a scholar assistant in Agronomy; from 
February, 1916 to August, 1916 as a graduate assistant in Agronomy; from 
August, 1916 to July, 1917 as assistant in Agronomy; and from July, 1917 to 
September, 1918 as instructor in Agronomy. In 1918 he was appointed by the 
Board of Regents of the University of the Philippines, a traveling Fellow for a 
period of two years, and entered the University of Illinois as a graduate stu- 
dent the same year. He was elected to the Illinois chapter of Sigma Xi in 
May, 1920. 



